I, too, am a 10+ year SmarterTools customer currently running v15. Although when I do upgrade to v17 I believe I'll do it just like any previous version upgrade with the typical uninstall/upgrade install, I see your concern and your request isn't really that far fetched. ST could easily, I'm sure, give you an extended trial key. The fact that a customer who's given ST untold thousands of dollars over the years gets little more than a shrug over a request is disheartening. I treat my clients as I would want to be treated and go overboard for my clients as a rule.
As as aside, I've been going to the same independent auto mechanic for years and years. Recently, my car was going to be up on the lift longer than expected and I had a meeting to attend, if possible. Owner of the shop offered to let me take his own car which I declined although he was earnest in his offer. That's service. Now, the kid who pumps gas can't offer the boss's car but he could ask his manager...
Don't want to make a mountain out of a mole hill but I get your point.