I voted "only when they break", but this is yet another case of "otherwise, namely".
First of all, I'm a mere amateur. Participating in a bluegrass session last month marked my first public appearance on bass in over thirty years.
As always, I tend to be verbose. Yes, I take the poll to be about "consumption" of strings, and instead I illustrate my considerations for [not] replacing factory strings.
I bought my first basses in 1981. I mainly used them at trad. jazz sessions, and was heavily influenced by the tone of upright basses and the staccato plopping of brass basses.
I replaced the factory round-wound strings of my Ibanez MV-924 with flat-wounds (Ernie Ball 2802). I think that these are still on.
I replaced the tape-wound strings on my acoustic Eko Chetro with the same EB2802, in order to have a magnetic sound-hole pick-up add low to the sound of an acoustic stick-on transducer. I have recently restored the factory situation.
The last couple of years have had me add five basses. First came an acoustic Fender CB-60SCE (featuring a piëzo bridge pick-up). I equipped this with flat-wounds, as it happens Dunlop DBFS45105. I have bought a spare set of these, too.
Then an electric Harley Benton MJ-4EB. I have promised myself to retain round-wounds on this one. It still features the factory ones (D'Addario, maybe NYXL), and I have spare NYXL45105 for it. I circumvened my promise by buying an MJ-5EB and fitting it with flat-wound Thomastik JF345.
Time for an acoustic 5-string (with piëzo bridge pick-up): Harley Benton B-35. I mounted round-wound Thomastik AB345, only after pointing to the flat-wounds on that Fender and the JF345 on the MJ-5EB.
Last in is a cheap short-scale P-type: Harley Benton PB-Shorty. It may have D'Addario EXL220S round-wounds, and that's what I have as spares. (Already I've been checking short-scale acoustics, and I might buy a second PB-Shorty for flat-wounds.)
The Dunlops mark the end of buying strings as incidental disposables for a given instrument, "chosen" to the instrument vendor's suggestion. Since then, it has been a matter of buying "pairs" of instruments and sets of strings.