I buy new bikes (actually just custom frames) when there is something I want to do that my current bikes do not do well. (My first ti custom to be the sweet riding ti bike that fits like a dream; something I've always wanted since I rode around the block on a Merlin in 1990. My second ti bike to be a pure road fix gear, not a winter/rain/city fix gear that could go anywhere and weighed 28 pounds. Fenders and U-lock.) Wheels - I've built my own the past 45 years except the pair on my first good bike and later, my race bike. Occasionally I'll see a wheel in a shop with a hub and rim I want. When I get time, the spokes come off and it gets rebuilt with my preferred spokes and pattern.

I love working on bikes. It's a joy. It's therapeutic. It (usually) saves me a bunch of money. And I love riding the results.