I hadn't gotten a haircut for longer than usual, and then Allison went abroad for almost a month, which bought me a lot more time avoiding a haircut. So I hadn't gotten a haircut in well over two months. Then two things happened:
Our friends Mike and Esther had us over for dinner (delicious!) and Esther asked me whether I had just woken up (given my messy hair). Then we started talking about my hair and how I had let it grow because when short Allison would complain that it was too short, and now I didn't know what to do with it because she was complaining it was messy. Then Mike, half-spaced out, asked for clarification as to whether my hair right now was right before or right after a haircut. Esther laughed vigorously of how clueless her husband was given how bad my hair looked.
So the following weekend I got a haircut while Allison was out in SF, not telling her, to see what happened. When she returned, we walked over to town, had a very nice dinner together and walked back. She never noticed that I had gotten a haircut, after so much complaining. That was on a Saturday. Today is Tuesday night and she still hasn't noticed.
Lesson reinforced: haircuts are overrated.