I've never had a bass I'd never sell. I got a '91 Thumb on eBay a few years back for about £600. That was the bass I'd always wanted, and I played them a lot in shops in '91 when I was a beginner. I sold it last year. It was an amazing bass, played like nothing else, sounded like nothing else, but ultimately it was just a piece of wood.
The two bass guitars I have now are basses I've assembled myself. They both have issues (the J is heavy due to a Moses neck, the P has a body that is basically scrap) but they sound right and feel fine and I don't really desire anything better. I think people can get too hung up on this stuff to be honest. Just play what you've got and concentrate on the music.
Last weekend I went to meet up with three guys I was in a band with in sixth form back in 1992 and we played our old demo. I had a Godin Acoustibass fretless at that time which sounded great but I was more pleased with how tight I was and how adventurous my playing was when I was 17 and I'd only been playing a couple of years. Concentrate on playing like a teenager is my advice.