I don't have anything to cite, but I would try to have the computer in question having long periods of idle time, so that the SSD has time to run garbage collection.
I've got an SSD in my server that runs the first version of Windows Server 2008, which didn't include TRIM support. It runs 24/7. I haven't noticed any performance drop-off, but then it isn't worked very hard either.
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I concur with Cerb. The first (definitely not low end) boards I saw with AHCI support were in 2007 (according to the dates on the manuals I downloaded at the time), the M2N-SLI is the first one I can think of that I used with AHCI support. My Athlon XP board from 2003 had SATA sockets on it.