Added 3 minutes later
The closest analogue to Heroes is chess, and in no serious chess tournament do they play with unlimited time, nor do they offer more control than in classical chess. Plus, there are many tournaments with shortened time controls. If you want to think calmly, you can analyze games, play correspondence games, create puzzles, etc. But in tournament games, time control is a serious strategic element that requires appropriate attention. I don't see any reason why it should be different in Heroes.