But that's the thing - there seem to be always new sources of SUBs if you want to spend the time to keep abreast of the options. For example, even with Amex and their famous "one SUB per card per lifetime" - it's not actually that strict. They OFTEN have "no lifetime language" card offers, and they still give out retention bonuses. In one of the funniest things that happened to me this year, I have two Platinum cards (back when you could get a separate SUB for different flavors of Platinums) and I had always planned to downgrade one of them to a Gold. I called in, they offered me an OK but not compelling retention bonus, so I downgraded to a Gold (a card I didn't have yet, and now with the one family rule I can't get the SUB on a new application anyway so why not), thinking I can then use the multipliers. Less than a month later, they gave me a HUGE incentive to REUPGRADE my card back to a Platinum - I can't remember what it was, something like 120,000 points. So I obviously re-upgraded and took the points (which were FAR more than the retention bonus they had offered me a month earlier).

Similarly, there are new cards coming out from other banks - like BILT, which has done a ton of crazy 2x transfer bonuses from time to time. And there are referral bonuses with Amex that don't seem to go away. And you can keep getting SUBs for business cards with Chase for some reason (though that's 5/24 and they're getting prickly about continually applying for new business cards).

Combining all these things it's certainly possible, without extreme effort, to accumulate enough points to cover a few very nice vacations every year.

But yeah, as it is I have to bend over backwards to use the Resy credits - though you can split the bill on two cards and that works well enough, but also Resy is pretty good in LA so we don't mind using it twice. I wouldn't want five cards with Resy credits, though.