I try to avoid excuses, as it can catch you out.
The OH works specific hours in the morning, so I know there's a window although I try not to abuse it and may visit someone every 6 weeks or so. As a rule I try to combine a punt when I am staying over night somewhere so it's more relaxed for me, or if I am enroute somewhere and build in the opportunity.
My biggest fear is having an accident somewhere where I am not expected/supposed to be, or picking up a speeding ticket meaning questions will be asked. Luckily I've used an unknown (to her) email address for the iPhone, so cant be tracked. Plus she's not that tech savvy so cant download my phone's GPS data. And neither do I use a sat nav for finding WGs addresses.
She did ring once when I was balls deep in a Thai girls arse....told her later on that the phone had slipped down between the car