The funny thing is that most young players don't "burnout" from playing too many, professional tournaments. It's the insane number of junior tournaments they're allowed to play at the same time.
The ITF seems to think these rules are perfectly fine for juniors:
13-year olds can play a total of 10 tournaments; plus 4 if they can reach a top 50 rank in juniors.
14-year olds can play a total of 14 tournaments; plus 4 if they can reach a top 20 ranking in juniors.
15-year olds can play a total of 16 tournaments; plus 4 if they can reach a top 20 ranking in juniors.
16-year olds can play a total of 25 tournaments, period.
17-year olds have no restrictions as to how many tournaments they may enter.
They're just as much --- if not much more --- travelling, physical wear, etc... on the junior circuit, than a pro would ever have to deal with.
Why this contradictory, and hypocritical attitude by the WTA/ITF regarding juniors and pros.
Think about it. Because young players are greatly restricted in terms of how many pro events they can play; many probably feel increased pressure to perform well, knowing that the margin for error is very limited. If they can't play against pros --- gaining valuable experience --- they're reduced to entering a vast number of junior tournaments to get playing time. This can be greatly detrimental to promising players, who have excelled at the junior level, and have learned all that can be learned from that level. It isn't helping them any, by forcing them to remain static; and restricting them from making their own choice as to when they're ready to turn pro.
The ATP only places restrictions on 14 & 15-year olds. Once you turn 16, you can play an unrestricted number of tournaments. They don't seem to have a noticeable problem with "burnout". Plus, you have to factor in the notion, that boys physically develop LATER than girls. All this coddling of female players smacks of gender bias and sexism. Girls aren't capable of playing more than men at an earlier age; they just aren't ready mentally, or physically. Bullshit! A 16-year old girl is physically mature --- has reached adult height and weight --- and mentally ready to make that decision on their own. If people feel, 16-year old boys can; why not girls?