No, I just thought it was a tad unrealistic that *everybody* (except Kirk, and even then there's the Shatner books) is still around, aged, like 200... And I figured Scotty deserved an appropriate exit, if it stays as an exit.
I have to agree with you regarding the survival of the TOS characters. At least with Spock being part-vulcan it was still plausible he would still be active.
I thought I had read somewhere the typical human life-span in the Trek universe was ~120 years old, however in Fragments & Omens from the DS9 relaunch it is indicated the life-span for a human is ~150 years.
By 2383 - Uhura, Sulu (if he is still alive) & Chekov would be in their late 140's & McCoy would be late 150's. If the typical life-span is 120, by now most of them (if not all) should have been dead by now. Even if the life-span is 150 it is very unlikely they would all still be alive and as active as they are. However, except from McCoy, have any of the others been heard of since the Watraii affair (2377?)? So it is possible they could have passed on since.
At least with Scotty it was realistic that he was still active due to the 75 years he didn't age, which would have only made him in his mid-80's. IMO I like the ending you gave to Scotty.