I've always changed my strings one at a time, but my tech takes all strings off at once and gives the bass a good cleaning. Is it bad to take all of your strings off at once? I've always heard it was.
i take off all strings when i change them. makes it so much easier to clean the bass properly and give the fretboard some cleaning and care
when i put the strings back on the pressure is back where it was before and things are in balance again..
i would not leave a bass without strings on though. the pressure the trussrod puts on the wood should be balanced with strings pulling the other way.. imnsho its my internet opinion, treat it as such
All at once or one at a time, it does not really matter. As expressed in the words of that famous and well respected gentleman from the south - just Git-R-Done!
Depends in the situation... if I'm just changing strings for a short-notice live gig or session where the "Zing! String" tone is called for, one-at-a-time is perfectly fine. However if I'm doing a "big" job of a full cleaning of the nooks 'n crannies & intonation/set-up, usually I'll strip them all off, oil all my Rosewood & Pau Ferro/clean my Maple fretboards, and reinstall the new set. All but two of my Basses have multi-piece necks, so I'm *negatively* worried about those compared to the two that have 1-piece necks... of which I have *no* worries.