Like, with Annelise, the impression I got was that it was only a periodic thing, not something that would require the same extent of juggling as a source like Martha. The trouble with Martha is that she's a fake-girlfriend and then fake-wife, and SHE doesn't think there's anything unusual about "Clark." So the "I'm busy at work" might be a good excuse for "Clark" to only see her once or twice a week, but he still has to be available occasionally, call her, etc.

With Annelise, it's a pure affair and Annelise is married to someone else. Philip's cover is that he's a spy for Sweden, so one would assume (or perhaps Annelise would) that he's in and out of town, etc. So probably he could get away with only seeing her a few times a year.