I only change my strings when I start thinking to myself, “my bass doesn’t sound the way it used to” or, more likely, if I simply fancy a complete change of brand/string type.
I’ve just realised that in 10+ years of playing I have never replaced my strings with a fresh set of the same strings I already had on! I seem to always use it as an opportunity to try something new. I guess, being a mostly casual player, I don’t have the pressures of gigs or recording sessions etc holding me to any standard of tonal consistency…so I’m just enjoying the journey through the world of strings at present.