are you sure that was not alcohol induced loss of direction???
All SV almanac data is updated every 6 days and is valid for upto 6 months, each SV sends data for all SV's.
Broadcast data is updated every hour and valid for 4 hours
each SV also sends only its own ephemeris data
this is why if you travel more than a few hundred miles the almanac data will be innaccurate and the GPS will not get an immediate lock, depending on the cylce of 30 mins you may have to wait 29 1/2 for a fix!!