I have an old used and abused K-750 and it would do 100kph while dragging a sidecar on 100-150 mile trips. I would stop about once every hour. I think that's the most either of us could take of the other at any one time!
The SV did blow up after a couple of years, but it was never really in great shape when I bought it! I was surprised it lasted as long as it did.
If you rebuilt it right, put in solo gears, and drove it as a solo, it'd probably last forever at 100kph.
That's my plan to do with an M-72 if I ever get the time, space, and money!
1959 KMZ (Dnepr) K-750 (Happy now?!?!?)
1962 KMZ (Dnepr) K-750M
1959 IMZ (Ural) M-72M