As long as it's working fine and you enjoy riding it there's no reason to be in a rush to replace it. I see lots of people riding some pretty beat up bikes that clearly have some maintenance issues. Wobbly wheels, nasty squeaks, disconnected brakes and shifters, etc. Your bike is much better than those, even if they were decent bikes 30 years ago... and the folks riding them don't seem to mind too much.

I'd never recommend that somebody ride a bike in as bad of shape as some of those, - especially when it comes to brakes, but my point is that it's all relative and none of it matters as long as you're happy with your choice.