On any reasonable sunny day an experienced pilot can stay airborne for several hours. During cross-country flight, or in competition, you try to always be in range of an airfield. If you have to land out it is usually not dangerous, you give yourself lots of altitude to pick a field and land there - sailplanes can land at about 40 knots and the landing distance is quite short. Sailplanes have large spoilers, or flaps that can be extended to as much as 90 degrees, allowing the pilot to approach a landing field with lots of reserve altitude and bleed it off very quickly if necessary thereby making the approach to land having lots of margin for misjudgment of altitude or wind velocity. A wind blowing onto a ridge will cause the air to rise up over the ridge and a sailplane can ride along just above and in front of the top of the ridge where the maximum lift is.
Gliders can fly hundreds of miles along ridges, for example, in Pennsylvania.
The only type of lift in Ontario. As the sun heats the ground, a rocky area, or a farmers ploughed field, the air is warmed and becomes lighter than the air around it. It forms a large bubble which breaks away and is called a thermal. As the warm bubble rises into colder air higher up it rises even faster. Eventually the warm air is cooled by the cold air several thousand feet up and condenses into a white cumulous cloud.