People may not be getting the unit into autolocate correctly. People are not waiting long enough. It takes 12.5 minutes for all of the almanac to be broadcast by the satellites. It can take MultiTrac 15-30 minutes just to find a satellite in AutoLocate. As such waiting an hour is not unreasonable.
Crystal oscillators drift over time.
The GPS receiver retains the oscillator information so that it can acquire when it is turned on. If this information is cleared it could take much longer to acquire in the first place. We tried this method on an old GPS 90 and, because the drift was so far out of spec after 6 years the unit had to be re-calibrated in a temperature chamber before it would acquire again. On the other hand, we used an old GPS 38, turned it on with fresh batteries, DID NOT use autolocate mode. In 4 hours the GPS 38 had healed itself through patiently looking for satellites.