In the next season, Cecil played in all of Boston's 44 games again. He made three shutouts and he had a 2.19 goals-against average. Thompson made much less shutouts and a much higher goals-against average because the rules were changed so that players were allowed to pass forward in the attacking area. That season, Boston won all but six games, finishing with a 38–5–1 record, which is the highest-ever winning percentage of any team in the NHL. In the playoffs, they lost two games in a row for the first time in that season. The lost the Stanley Cup finals against the Montreal Canadiens. Earlier in the playoffs, his streak of winning his first seven games was ended. It remains the longest winning streak to start a playoff career. Thompson won his first out of four Vezina Trophies that season.
In the 1930–31 season, he played all 44 games again, and was named to the Second All-Star team. In the next season, Boston lost the semi-finals of the playoffs to Montreal. In the second game of the series against Montreal, Thompson was removed from the net near the end of the game. That was so done so Boston would have six attacking players against Montreal's five. Having more attacking players gave Boston a bigger chance to score. Although Boston lost, their coach's idea was described as "amazing".
In the 1931–32 season, Boston did not play in the playoffs for the first time when Thompson played for them. He missed five games during that season, which was the only time that happened to him. In the 43 games he played, Thompson won only 13. The next season, Boston made the playoffs again, but they lost to the Toronto Maple Leafs.
The last game of the playoff series against the Maple Leafs was described as Thompson's best. In that game, Boston and Toronto were tied after three usual periods of 20 minutes. Since the game was tied, it proceeded to overtime. After five periods of 20 minutes, the game was tied. At end of the fifth overtime period, managers Conn Smythe of the Maple Leafs and Art Ross of the Bruins ask the president of the NHL, Frank Calder, to stop the game, and finish it later. Calder refused. Early in the sixth overtime period, a pass from Boston player Eddie Shore was intercepted. Ken Doraty of the Maple Leafs went for a breakaway, meaning that he had the puck and was skating toward the other team's net with out any defender between him and Thompson. He scored on Thompson at 4:46 of the sixth overtime period. Even though he lost the game, he was applauded loudly by the fans at Maple Leaf Gardens. This game was the second-longest ever played in the NHL. Even though Thompson lost more games than he won in the playoffs, he finished wit a 1.23 goals-against average.
Thompson got his second Vezina Trophy in the 1932–33 season, making 11 shutouts and getting a 1.76 goals-against average. The next season, Boston missed the playoffs. In the 1934–35 season, Boston placed first in the American Division. Thompson was chosen to the Second All-Star team for his second time. The Bruins won only one of their four playoff games. Their only win came when Thompson had a shutouts. He finished the playoffs with a 1.53 goals-against average.
In the 1935–36 season, Thompson made 10 shutouts, but Boston won only 22 out of 48 games. During that season, Thompson made an assist, meaning that he had made a pass on purpose to a teammate, who scored a goal as a result of getting the puck from him. At that time time, it was very rare for a goaltender to do that. At the end of the season, he was named to First All-Star team for his first time. He also won the Vezina Trophy for his third time. In that season's playoffs, Boston's series against the Toronto Maple Leafs was a series of contrasts. Boston lost the two-game, total-goal series eight goals to six. In one game, Boston won against Toronto 6–0, but they lost the other game 8–0.
In the 1937–38, Thompson played his last entire season with the Bruins. He won 30 out of the 48 games, but Boston lost to the Maple Leafs once again in the playoffs. At end of the season, he won his fourth and last Vezina Trophy, and was named to the First All-Star team for the second time.
Thompson played only five games in the 1938–39 season, because the Bruins decided to replace him with Frank Brimsek. To make space for Brimsek, Thompson was traded to the Detroit Red Wings for Normie Smith and $15,000. Thompson also received $1000 from Boston. Art Ross, still the manager of the Bruins, predicted that Thompson would play five more years for Detroit; however, he only played two. Although Detroit lost more games than they won, they made the playoffs in both seasons, but they did not win the Stanley Cup. Overall, Thompson appeared in 85 regular season games for Detroit, recording a 32–41–12 record, seven shutouts, and a 2.54 goals-against average, and in 11 playoff games, posting a 5–6, with one shutout and a 2.41 goal-against average.
After stopping being a professional player, Thompson became a coach. In the 1940–41 season, he started to coach the Buffalo Bisons of the American Hockey League (AHL). He coached the Bisons for 56 games in two seasons. They missed the playoffs both times. In the 1940–41 season, he played one game for the Bisons as an emergency goaltender.
During World War II, Thompson served in the Royal Canadian Air Force (RCAF). He was also the coach of the Calgary RCAF Mustangs of the Alberta Senior Hockey League. He led the Mustangs to the league championship series in 1942–43 against the Calgary Currie Army team. In March 1943, injuries to the Mustangs' goaltenders made him play again. With Thompson in goal, the Mustangs won against Currie Army, 8–4, to tie the best-of-five series at two wins each. He played the deciding game, but his team fell short of winning the Alberta title with a 3–1 loss.
After the war, Thompson became chief Western Canada scout for the Chicago Black Hawks. He was one of few scouts who tried to find a player's personality along with their playing skills, often talking with players as part of efforts to learn about the players he was watching.
Thompson was stand-up goaltender, which mean he rarely fell to both knees to try to stop the puck. He was one of the first goaltenders in the NHL to catch the puck in order to stop it. He was the best puck-catcher when he played. With gloves smaller than one of other players, Thompson did not have a lot of padding when he was in net.
He often used the same, or very similar method, to stop pucks. He dropped to one knee with the paddle of his goalstick covering the space between his legs, and extending his glove to cover the left side of the net. Although he caught the puck with his glove, he did so without gloves that were like the modern blocker and trapper. The blocker is a glove which is worn on the hand which holds the stick and is used to hit shots on goal back. The trapper is a glove which is worn on the other hand and used to catch shots on goal).
Thompson was described by Johnny Bower, a former goaltender who was inducted into the Hockey Hall of Fame, as being able to play the puck well with his stick, and one of the best of his time at passing the puck. In the 1935–36 season, Thompson became the first goaltender to get an assist by intentionally passing the puck with his stick to a fellow player.