Switching to Full-Time contracts: who and when?

So...

I'm at the beginning of my second season at Keflavík in Iceland, and I'm gradually switching to Full Time contracts as soon as a contract renewal is needed for my starting eleven and hot prospect.

However I'm also working on a very tight budget [both transfers AND wages], so I can't really afford to offer FT contracts to every player, especially since Key Player want something around £50.000/60.000 p/y...

So I was wondering... Is it really worth "upgrading" the contract to a player who, according to my staff, has already reached his full potential and is in the 28+ age category?

I mean, sure a FT contract will give him more training time, but what's the point if he can't get better than he is?

Will at least his decline be less dramatic?

Or should I just offer FT contracts to younger players?

I usually try to get all my players on a full time contract as soon as possible as i believe having them all on full time contracts helps the club go from amateur/semi profesional to professional quicker (i am not actually sure if this is true or not). I also think it gives you morew chance of getting a decent fee for them if someone makes an offer.

I wouldnt know for sure about wether it decreases the rate of decline or not. I think though that realistically someone training full time will keep there stats at higher level for longer than someone who only trains part time.

If a player is on a full time contract, he will train full time, thus increasing his attributes faster than on part time contracts. The same with coaches. If they are on part time contracts, they will spend less time training the players.

Hope this helps!