so is there ever a good time or certain conditions to train the team as a whole?
Generally, other than free throws and stamina, which are only available as team training, it's widely recommended to never do the other training types for the whole team. It just doesn't train quickly enough to be worthwhile, so you end up with a roster of players who are improving very slowly and not nearly enough to make a noticeable difference. Usually, you're better off training guards or big men, and then using veterans in the other non-training positions. Your team will improve as your trainees do, and then you can replace veterans with better ones as time goes on when your economy allows it.