Windows 7 supports the TRIM command, which results in free space being usable by the SSD. Unless you have an old buggy Sandforce-based drive, or an even older Indilnix-based drive, that truly do need actual erasing for performance reasons every now and again, you shouldn't need to worry about it.
So, if you're on Windows 7, using either Intel RST (iastor) or MS (MS standard AHCI or ATA controller) drivers, no worries. If using Vista, check and see if there is a toolbox program for your SSD (I'm not sure if IRST supports TRIM on older chipsets or not). If it includes a manual TRIM option, use that every now and again. If running XP, please get to 7 or 8.1 before April, and stop worrying about silly things like secure erasing SSDs 🙂.