This thread lets me drag out one of my favorite "old timer" stories. Back in the good ol' days (early 2000s), you could buy US savings bonds with credit cards directly for a while. No fees, no cash advance. Risk free, and interest rates made it worthwhile (about 5%) (plus miles on the purchase, of course). I bought a bunch (maybe $20000 worth or so eventually) that I was able to float for nearly the entire 5 year vesting period through stringing together a series of introductory 0% (no fee) balance transfer cards. I think I eventually got tired of it, and interest rates dropped, and it got harder to find new BT cards. Fun while it lasted.

But there's no way I'd go through that hassle for the 1% margins the OP is talking about.