I'd say my most durable retro steed is my dbr axis tt. Yes it is ti, but possibly one of the best retro ti frames of its time, made by sandvik. Not seen any that have cracked or broken, unlike some retro ti.
I've built and rebuilt it many times, my last/current build saw it shed the uber reliable xtr m952 groupset in preference for m970 xtr, just because I had a new groupset I had mounted to an sts, but never actually used it.
I also went with rigid pace rc31 ti forks to keep it simple up front.
Retro ti post, bars, stem and bar ends were replaced with Thomson just because it is strong, light and reliable quality.
It rides really well, frame is light, balanced and strong. Gearing is in my view st least the pinnacle of xtr (and I don't say that lightly as m952 is my favourite retro ish gear). The rest just works and looks good.
Other parts that top it off are purple pauls v brakes, ti odyssey brake booster to stiffen up the rear, spinergy xyclone rim brake wheels and a flite tt csrbon/ti saddle.
All adds up to a nice lightweight, reliable and of course pretty bling retro mod.
The only thing I would change is the frame has a canti cable mount not in use. I did remove this on another tt frame I had, but not doing that to this one.