I'd say that if you don't wish to be held to a pledge like "once in a generation" then don't make it. If you're the sort of person who thinks words don't matter, that your promises and guarantees don't matter, then I get it.

Otherwise I would have to conclude that you simply wish your political goals to be made easier. We'd all like that.

I think it’s more about expectations that dishonesty. One might expect something is a once-per-generation event, but then things happen, stuff changes, here we are less than a decade later hoping to do it again.