Thank you for the feedback, everyone. I suppose devaluation is a concern that I'd have to take into account. I have a couple of questions:
1) Since I don't get to travel much, I'd hardly (if ever) be able to gain hotel points/rewards with stays. So the bulk of the points I acquire would be through SUBs. Does that change the equation at all, given that I wouldn't be putting much spend on the card beyond obtaining the bonus?
2) A stupid question: If you only begin acquiring points for an aspirational trip 1-2 years out, how on earth do you get enough points quickly enough to make it worthwhile?? Especially when it comes to these new Marriott cards, where you seemingly can only get a bonus every 24 months.
Item one does change my previous reply. If you're only earning points via SUB and not travelling otherwise, then you're not going to ever have the opportunity to casually use them for increased value as I suggested. In this case, I'd say go find something that suits what you want to do with them and use them up. However, it doesn't make sense to me why you'd pursue Marriott points if you don't travel much. It's would be like me collecting VS rewards points when I don't shop at VS.
As for question 2, you answered it indirectly with question 1. "Aspirational" travel on a 1-2 year plan isn't something you can apply your way to, excepting the churniest of churners who will find a way regardless of consequences. Even then, they're going to likely do it once in their lives. The thing with travel is that the more you do it, the easier it gets. Staying even 50 nights a year in a Marriott is likely going to earn you over 100,000 points just from the stay, and that's before any Megabonus or other promotions. Throwing those stays on a co-branded card will add another 50% to that total. None of my points came from credit cards. I don't even own a Marriott co-branded card.