Windows 7 has support for the TRIM command which should help ensure that the performance of an SSD drive remains good through it's life.
How can you tell if a given SSD drive supports TRIM?
See here for a description of TRIM.
Also the following from a Microsoft presentation:
Microsoft implementation of “Trim” feature is supported in Windows 7 NTFS will send down delete notification to the device supporting “trim” File system operations: Format, Delete, Truncate, Compression OS internal processes: e.g., Snapshot, Volume Manager Three optimization opportunities for the device Enhancing device wear leveling by eliminating merge operation for all deleted data blocks Making early garbage collection possible for fast write Keeping device’s unused storage area as much as possible; more room for device wear leveling.