While my ratios vary a bit too much for my liking from month to month (not the only one of my sponsors I'm seeing that pattern with though, and it's not quite clear from my own traffic stats and sources why it should happen), 21SexturyCash has been among my top 5 sponsors for more than two years (I started promoting Club Sandy when they were still a CCBill/Verotel sponsor, before they switched to a NATS system).
My overall ratio for 2007 so far is 1:765, and that was with a freakishly bad March (1:2880) and a not too great May either.
I'm mostly promoting their old sites though, Club Sandy and Pix & Video, plus a few of the more recent ones - Asshole Fever, Sweet Sophie Moone etc. - and I'm getting a fair amount of rebills (I'm currently at pretty much the exact same number of new sales and rebills this year).
I must admit I haven't been too thrilled watching them add all those new sites - it's damn near bound to have a negative effect on the overall quality (one of the reasons I've never really bothered much with the huge big name sponsors, though I'm obviously not saying all their sites are necessarily crap
), but fortunately at this point that only seems to be a concern for those new sites as their oldest ones haven't suffered (Club Sandy is still one of my own favourite sites).