I have run on the failover PIX for a few weeks. In fact it became the defacto active PIX it ran for so long. There was no reason to fail back to the active, so it was left as is, and ran fine with no issues. Having a time restraint on it wouldn't be very useful, what if you couldn't get the old failed active PIX up in 2 days, you would be left without a FW. Wouldn't make sense (support costs would be too high for some companies that way).
Hope it helps.
Steve
