Well, since YOU say it takes 4 years minimum, then that must be the gold standard, eh?
What does it tell the kids on the team that you took over when you say, 'hey, I didn't recruit you and didn't necessarily want you on my team...so give me 3-4 years to replace you with better players and then we'll be ok. For now, give me your best shot. Thanks, guys, now let's go have a good practice.'?