So basically you just need to admit you're hankerin for a new one.
Titanium would obviously be the likely choice in terms of frame durability. Then buy a bunch of replacement parts for whatever wheels and components might fail over 10 years or so, plus cables, etc.....
Trouble is standards change. The industry is moving to disc brakes, so potential for a harder time finding side pull pads ?, that may be really far out though. Wheels moving to thru-axles, so a spare rear wheel ?, certainly cables, cassettes, chain. Systems up to 12 speeds ?, can we envision more ?, but who would have thought 30 years ago when 7 was all the rage that we'd be at 12 rear gears now, plus the sometimes silliness of 12 rear and a single front. I think though that we will see a return to BSA as a b-bracket standard.
I used to think "this is maybe my last road/mountain bike", then realized that's not going to happen if only as the newer technologies can improve riding and I'm a sucker for new stuff. Maybe when I'm 80 and REALLY seeing my riding taking a decline will I consider planning for my "last bike".