The idea that SSD's have a limited number of write cycles in them is now not so true any more, depending on the SSD you've got. It was definitely true a while ago, but the technology has improved quite a bit since then. Here's a good article on it:http://www.storagesearch.com/ssdmyths-endurance.html
That guy cautions that not all SSD's are as good as the one that he did his calculations on (and got the answer of "it would take 51 years to wear this out even if you were maxing out write cycles continuously") and he's probably right, but I still don't think it's much of a concern.
For my part, I've been using a cheap little USB stick (I got it for free at a conference, so it's probably the cheapest, crappiest kind of flash out there; its performance is terrible) as an off-site backup device for the last year or so. It has an encrypted filesystem on it, which is probably quite stressful to flash because it scatters writes all over the place by design, and on top of that I fill the drive all the way again and again. It still works just fine, not a hint of bad blocks.