They couldn't.
Looking at all the dreams presented here i really wonder how few people actually realise how dead in the water the post soviet everything(and i mean everthing) was.
It's possible, but I doubt it. I think it's more that if/when they had to go up against a serious opponent (such as NATO) they had enough aircraft that even with poor readiness rates they could count on enough being operable for the four weeks the campaign would last (after that, either they had won or the nukes had flown).
No, I mean that the reason they had so many aircraft is that they expected them to be used up. Although if they were planning to use trainers, they weren't the only ones: the RAF was planning to arm their trainers and use them with instructor pilots as last-ditch interceptors, and I'd be amazed if most of the Eur0pean powers didn't have similar plans. If Big Mistake #3 kicks off, you need to win before the nukes fly, or everyone loses. There's no point holding anything back for training if it won't get to the front in time to be useful.