I know exactly what you are saying. I found my 'Wife (!)' bass a while ago (didn't know it then) and had always owned at least two fretted basses at the time. The beauty of this is that you can spend some time with both and sell the least fave for another top end bass (careful baying/selling will not lose you any cash) and over time it became clear that my 'Wife' bass was beating the competition hands down. All the while I had been playing it live, recording with it, making bumps and scratches on it and generally living with it and loving it.
Somewhere along the line (about 6 or 7 basses into my 'comparison') I became bored of selling/buying and the hassle of it. I sold the competition and settled down with my wife (and her fretless sister ) and couldn't be happier. I am totally comfortable with the bass in any situation due to the time I have had it and have managed to compare it against every other bas I have fancied. That, mixed with the rarity and uniqueness of my instrument, meant that it became 'me' and 'my sound'.
So - if the '88 is comfortable, works for you and feels like the one, keep it and start comparing it to other basses when you have the money/time. You might find something else, you might realise that it is 'you' - there is no way of telling until you have a try. That way, a few years down the line, you can sit back with your '88 happy in the knowledge that it is part of you and your sound, in the same way you wouldn't want someone else's eyes or summink'
Cheers
ped