One of the odder factors about the way the SCCA handles safety equipment specs has to do with aging. We do enforce harness aging per SFI and/or FIA requirements. However, we really don't do much else with aging. If an aging rule is in the main GCR, we enforce it.
The reason this is odd is that most safety equipment standards have recertification rules. A good example is fuel cells; the FIA FT-3 spec calls for recertification of a fuel cell at 5 years, and limits the use of the bladder to 7 years, max. Since the GCR calls for Fuel cells per FIA FT-3, probably we implicitly have this age limit in a strict reading of the GCR -- but I've never enforced it that way, nor have I ever seen anyone seriously attempt to do so.
Window nets are no different; there is a 2 year recertification rule embedded in the current SFI spec.
If you go to the SFI Foundation web site and click on Specification List, there's a table which shows the recert periods in the right hand column. On the FIA Web site, the standards are here and here. The recert info for FIA standards is not broken out conveniently, but is buried in the specs. I didn't know what the aging rules were for FIA FT-3 until I downloaded the pdf and read it. I don't recall ever having been encouraged to do anything like this in the 14 years I've been an active tech inspector.