Everyone's perception of value is different. I can only tell you where I stand. I would give a definite "yes" to sticking with Stainless. As for upgrading every 3-4 years, that's pretty much a given with a smartwatch. Probably by that point the battery is going to be getting high in cycles anyway.
The incremental cost of going with stainless is not a big deal to me, but the enjoyment of wearing something shiny and classy-looking is a big deal. I'm going to have that on my wrist every day, for business and pleasure. I want to admire it. I want others to admire it.
I started with an aluminum Apple Watch in 2015 and ended up returning it for the stainless within the two week return window, because I realized pretty quickly that I wanted something nice on my wrist. The Sport watch was decent but mostly looked utilitarian. Once I replaced it with the SS model, I felt really good wearing it. Heck, a few months later, I went the full monte and purchased the stainless link bracelet, which is now attached to my Series 2 and will probably end up on a Series 4 and maybe a Series 6, because unlike the watch body, the bracelet does not need to be replaced. Just refinished from time to time, perhaps.