One does not need the "best and lightest" tuners, *but* I have had a very bad experience with Gotoh Y tuners replicas on new basses, which would break/slip forever on the first string change. Unacceptable. Though all brands can fail, I rather work with reputable brands such as Hipshot, use real Gotoh parts, etc. On the other hand, if you have a used bass with perfectly working tuners, unless you hate the way they turn, their looks, etc. one may as well stick with what works. I had super worn stock Gotoh copies on a bass 25 years old, and they *never* ever malfunctioned-were changed because their age was showing on its looks, and the turns could have been more precise-I doubt sticking to these old tuners would have been technically problematic, and I just changed everything to match the look of a newly added Hipshot Xtender.
In short, if it works well and you like them, no reason to switch to a groupthink approved brand-but I would never buy cheapest among the cheap tuners for any bass due to my bad experience with the aforementioned, factory new basses.
I do not think you must change tuners for all your basses if they are performing well. Hipshot won't make the bass necessarily better. It may make it lighter, heavier, or smoother a turn, but it's not such a big deal, unless you are wary of possible failure due to extreme cheapness of manufacture.