@simao the advice on Tube Rolling from @mulveling is solid, there is a very good experience to be had from experiencing how a swap out of a Valve can influence a end sound being produced.
Running this experience parallel with your interest in vinyl replays will bring dividends.
400 LP's is a nice collection, the chances of playing one daily is unlikely, so there is plenty of choices for a listening session to be listed and getting on with and the odd new addition which is inevitable.
When I listen to Vinyl, I usually select 10 LP's to be used over a few days with my Wife, and as the Selections are played over a few periods, there is always one or two sacrificed for a new choice that is made, could even be a CD is the only Album available of the one desired to be played.