Nowadays for bikes& cars its not mileage thats the crucial factor-as already said metallurgy has come a long way since the 70s.
Take two similar bikes. First one has done low annual mileage,spending winters in shed,battery discharging,oil affected by cold & damp-with no protective treatment to surfaces,fasteners.
Second example ridden regularly,cleaned,treated with care.
Then theres the service history---the "paper trail" so to speak--that can tell you a lot.
So each case on its merits or otherwise.
example. Both bikes bought by me last year. Blue FZS 600 33k miles one owner.Had been ridden all year round. Bike clean & roadworthy BUT front of engine/underside never cleaned so corrosion of exhaust studs,nuts,headers,collector box,pipework & rad quite advanced. At 10 years old I spent quite a lot to put things right.
2nd bike 10 year old FZS 600, 3 previous owners,the first two only did summer dry miles & then 3rd owner did 5k miles in 12 months. I bought bike showing 12k & it rode like new.
So look for evidence of care, because its things like condition of fasteners,electrical connectors that tell you a lot,apart from all the obvious signs of drops/crashes.
Dealers use their "bible" of bike prices when doing trade-ins part exs and like cars most vehicle values drop off the scale at 7 years old.
The life span of modern machinery is more likely to depend on the cost of expensive/complex electronics failing which it will do eventually,making repair uneconomic.
In a nutshell I wouldnt be put off by high mileage if there was enough evidence of proper servicing/care. Its as important to assess the owner with some purchases as it is the machine!