The one hour rule comes from the standby requirements : if you are on home standby and you are called out you have 45 mins from the phone call to prep and leave the house and then 1 hour drive to the airport ie 1hr45 mins total. Exactly where on the airport you have to get to isn’t clear …..car park, checkin desk, FBO ?? However, in 14 years I have never once been called with minimum 1h.45. If you live 1.20 away then I wouldn’t sweat it too much.