I help with the training of a group of local junior players, from a fitness-training perspective. I do some coaching too, but not usually of this group, I coach some younger players and some beginner adults. Of late I've been sorta helping coach them, a little by default. I'm keen to hear the opinion of other coaches, especially the very experienced ones. My big goal for all of them is consistency, they are very much of the 'winners are what the game is about' mentality. I want to see them be able to hit 80% strength rally balls, deep, with directional-control and a safe amount of spin, over & over. Q: For a group of mid-teen juniors (14-16), what is a reasonable rally length to demand from two of these players on a court? Their level is probably between, say, 4.0 and 4.5, with one or two just below or heading just above. What about 4 players hitting in doubles mode? Different or same length? (Assume the rally starts from a feed, not from a serve, and assume hitting winners is explicitly banned - aiming for shots like the above, 80%, safe-deep, rally shots).