I’m another of the, “If it’s not getting used, move it on,” brigade. However, this has bitten me in the bum a few times (both guitars and basses) where I should’ve kept hold some pieces, but it’s all been a learning process which has brought me to where I am now. I have 4 basses, two of which are custom builds based on what I’ve learnt what I’ve liked over the years and these are likely to stay with me for many years (never say forever and all that). I can see improvements that could be made with the other two (just small things) but they’re getting used as is, so no plans to move them on at all either (Lady Ez has forbidden me to sell one of them as she thinks it’s really different sounding from other basses - it’s a Rob Allen). So I guess I do regard them as tools, but as many artisans take pride in their tools, I do too.