Best time to sell youths

I have a load of T players and am currently on ETF.. When's the best time to sell them for profit? Early on or will I make a good amount of money training them up to WK or further on?

Best ones atm are:

Links removed BW

.

.

Links removed as they're not necessary to the thread and it could be seen as advertising ...if you which to know the value of a player then use the valuations forum (and read the rules in there as players can't be on auction or T/L) with regards best time to sell, there isn't one really, depends how good the player is...Auctions I tend to finish as close to 11pm as possible