No lost data as it's backed up on the iPhone.Do you lose all of your app settings and workout activity data when you re-pair? Also, why does it take an hour?
TxWatch
It does take a while to pair and set up the Watch for some reason. Maybe not quite an hour, but certainly long enough that you don't want to do it often.
Watch from the last backup which is made when un-paring. This takes a little time to restored and it is the same as right before the backup.