Whether a player will max attributes by senior year, will depend among other things on
Work Ethic
Potential
You have complex choices to make - do you emphasize team practice for IQ or individual practice and which skills do you emphasize. Generally, among individual skills you want to focus on stuff that matters for the player's role. So, generally, for example, invest in REB for a Big but not for a guard - all things being equal
I think most folks spend between 20 and 25 mins on each of their offense and defense. If my team is all potentialled out - close to too many players maxing - I may even go a bit higher
Check the forums for old threads on practice and play around with what works for you with these general ideas in mind - and enjoy!