It's true that there is no way for Windows to know what drives are in your raid array and therefore no way to make it support trim on the array. The only way this could work, and I'll bet oems start doing this, is to have your raid controller support trim. Another option would be to make the virtual drive that shows up to Windows emulate the trim properties of the drives within the array. Obviously it could only appear as a trim-supporting drive if every drive in the array supported it. It would really require new transparency to allow Windows 7 to deal with the drives independently based on each drive's unique state. So, short story, they could change things to support trim in the future but, for now, you're right; there's no trim support for your raid array.
By "drive longevity" you could mean how performance degrades over time, or you could mean how long the drives will last before they die. I don't believe trim will affect the later. For performance, lack of trim will mean the array could potentially get slower as time goes on and you continue to read/write/erase. That being said, the Gen2 X25-M drives are drastically better at dealing with this without trim support than any other drive I'm aware of. The need for trim was almost superfluous on these new drives. If you're going to deal with no trim support, you've at least picked the right drives!
The optimizations that will help the most are disabling defrag, setting a fixed page file size and making it much smaller (to conserve meager capacity), disabling windows indexing service (again, save space and write cycles), and limiting or removing the system restore feature. I keep system restore on as I have a propensity for killing my machine pretty often.
I'd leave superfetch on. Superfetch may not be AS necessary as with a standard hard drive, but ram is still faster than your shiny new ssd array. Your most commonly used apps will still load faster with superfetch on. Turning superfetch off frees up drive capacity and ram, and minimally mitigates additional write cycles to the drive, so it's your call. It's interesting to note that those who had a normal drive with superfetch ON and moved to an ssd with superfetch OFF could actually see app launch times get worse for what I just mentioned. Granted, booting up and getting the superfetch cache populated would take forever on the normal drive case.
Let us know how it goes and what your performance it like!