That's about how I deal with strings, too. I mean, it's not like they cost $100 a set, fer crissakes! And as you say, the feel and sound of new strings is a wonderful thing.
As for the SS frets changing sound, I haven't heard any difference, either. But, to be fair, I've never put SS frets on a fiddle that had nickel-steel frets on it before so I've never been able to compare apples to apples. Still, I don't think there's a difference. I also don't seem to wear frets, but that could be because I've never had a guitar long enough for it to show up. Historically, it's been the rare instrument I've kept more than a few years. Grass is always greener, and all that. Plus, I've never been much of a collector so I don't usually add guitars, I replace them. That's changing lately - over the last couple years I've drifted up to 4 of them, with plans for more. In fact, I may be picking up a solid mahogany Warmoth Strat body today that some guy is sacrificing.
The one thing I have noticed with the SS frets is they seem to even the dynamics out if you hammer/pull/slide a lot. It's almost like a mechanical answer to a compressor/expander. Notes that you hammer on, pull off, or slide up/down to are typically somewhat diminished compared to picked notes, but on the SS frets that's less apparent. The dynamic range levels out. But, that could be my imagination.
If nothing else, they're dramatically smoother and easier to play, so for that reason alone it's worth a $20 or $30 bump.