Wear-levelling works against you?
Couldn't wear-levelling actually work against you in a RAID environment, by causing all drives to fail at nearly the same time?
Not exactly. Without wear-levelling a small subset of blocks would get hammered and the "disk" would fail a lot faster. RAID or no RAID.
However, there's a difference in failure mode between an SSD array where all devices will predictably degrade to unacceptable at about the same time, and an HD array where the future failure of each device is pretty much unpredictable unless you are suffering from common-mode failure (ie a batch of bad disks). In any case HDD failure is linked firstly to hours in service, and then to seek activity. Volume of data written to a HDD does very little that could cause earlier failure.
RAID nearly doubles or trebles the number of write actions. With JBOD, M writes spread over N disks. With RAID-5, 2M writes spread over (N+1) disks. With RAID-6, 3M/(N+2). This will reduce the SSD life expectancy in that environment by ~2x or ~3x.
With SSDs you might want to define a new sort of array that puts differing amounts of parity on different drives, so each SSD in the array experiences a different level of write activity and wears out at a different rate. Of course, there would be a penalty w.r.t. the performance of such an array.