I have had basses (Fender, Rickenbacker, and even a cheap Japanese with mandolin frets) that were over 30 years old, and the original nickel frets were still just wonderful. unless you play bass with a death grip (which, if you do, needs some attention to get resolved BTW) there is nothing wrong with nickel frets, nor is there any requirement to use stainless frets
and for the record - I have a couple Warmoth necks with stainless frets and one with the gold frets. on a bass, I can't hear the difference that a new set of strings (i.e. different brand or model) won't account for. definitely nothing that a different set of pickups won't easily walk all over. I also don't feel any difference outside of the different profiles, but then I don't play like Billy Sheehan (nor do I have his seriously lacking tone)
all the best,
R