I'm a big believer in "own your stuff" - follow your maintenance and storage guides, save digital copies of your manuals, call the 1800 hotline (they are super helpful!), get handy with basic (handheld!) elecrical and mechanical repairs, and share what you've learned.
That being said, the main reasons I replace what could be repaired are:
* a chance to upgrade something I bought 15 years ago
* cost of replacement parts is too high = most appliances fall in this category, very frustrating
* anything involving woodworking, it has never interested me but in hindsight I could've fixed quite a few things that just needed a new foot or bracket or even a whole drawer
Things I've replaced that were repairable:
Umbrellas, clocks, electric can opener, game consoles, IKEA bookshelfs and other furniture, carpets, hoses, electric tiller (part prices grrr), handheld vacs (part availability grrrr), a ton of kid toys that just needed a breadboard or piezo or light
Tldr Not as much as you'd think after 20 years of marriage, kids, and upward mobility, take care of your things!