I'm not sure I get the idea of a built for life utilitarian frame. Utility kills bikes, I've been through three and corrosion hasn't been the cause. I'm not riding the bike I had ten years ago, I don't have the same usage.
I'm intrigued by this. My current bike has belt drive, Rohloff, SON dynamo
My thirty years of utility bikes - First swap to fit a Rohloff, next was stolen recovered damaged, followed by cracked frame, change of use when I started doing deliveries, that one was written off by car, then when I started using an E-bike for deliveries I also changed my non assist bike to be more suitable.
The Rohloff has been a constant since 2002, though it needed converting to disc on a frame change and the current frame is belt ready so at some point I might also make that swap. It's also changed wheel size twice. The dynamo also needed swapping to disc.
Well done for getting 13 years out of your last one, belt ready frames must have been a rarity then and belt Rohloff's more so.
If you think you can choose a bike to last a lifetime, great. It wouldn't have worked for me at any time in the past and I'm doubtful it would in the future. My next change may be to go fully electric, though I'm hoping not for a few years.
I'm still of the opinion that if you can find an OTP frame that meets your needs and get ten years utility from it, it's likely to prove good value. OTP frames are often better than custom, it's an economy of scale thing, for example nearly all the steel frames coming from Taiwan and China have better corrosion protection, ED coating and batch finishing.
