Question: how long does it take to train in fallout shelter?
Answer: The higher level a dwellers' SPECIAL stat already is, the longer it will take to train to the next level. E.g., a dweller with 1 in Strength will only take about 25 minutes to reach level 2, while someone with 6 will take 6+ hours to reach 7. And you can't train beyond the maximum level of 10 in a single stat.