1 - it depends on how much writing you do, and what sort of writing. It could be anything from a day to a year. With an "average" enthusiast system used for gaming, my worthless guess would be a month or two.
2 - There are construction sites in Manhattan for the second avenue subway. The signs still say that the project will be completed in the fall of 2010. Think of TRIM in RAID like that.
What follows is unasked-for advice. You don't have to read it.
Why are you building a RAID of SSDs? It's appropriate in a very small number of applications, or if you just want to play around with it. RAID0 is simply inappropriate; buy an SSD twice the size rather than RAID two SSDs and you will get a better-performing system. If you are using RAID 1, there is a way that you can set up the mirroring in Windows that will give you the backup copy but enable TRIM. Of course, if you are planning to use a higher RAID level then the answer is not so simple.
Xbitlabs on RAID 0 of SSDs: http://www.xbitlabs.com/articles/storage/display/kigston-hyperx-ssd-raid0_7.html#sect0
Of course, Tom's did built a 3GB/sec (that's gigaBYTES) RAID of SSDs, but it was more of a technical exercise than a useful setup.