Other than budget or spouse that is. I've been buying instruments for over 40 years and cringe to think of the stuff I have bought and traded away. Saturday I ordered an Ibanez TMB35, a short scale 5 string that is only $250. Yesterday I canceled the order after finding out how hard it is to get decent strings for a short scale 5 string. Thinking back, that was a good thing. I've decided to self impose two rules for purchasing musical instruments.
1. For every item that comes in, two have to go out. If I want a new guitar: bass, electric or acoustic, I have to either sell or give away two. I have too much stuff. I don't need more items, I need more quality.
2. Any item I buy has to be at least as good as my best item of that type. I already have an Ibanez SR1405. Why make such a huge step down in quality? Yes the TMB35 is short scale, but could I really be happy with a $250 bass after playing $1400+ instruments? Just another item to stick in the closet.
There will be exceptions, like guitar pedals. Seriously, you cannot have too many guitar pedals. And they are small. Maybe a limit on how many duplicates. But, you have to keep it real.