That was a great idea, thank you!
I asked him if I could do that and he said yes, so I went ahead and did it, and it worked for a day. It seems as though only 1 of the sims in the house ever has the aging disabled on him when I check them all. He's only ever had one tattoo, so it doesn't make sense for him to never age. Would he be keeping everyone else stuck in their age as well, do you think? As soon as possible, I'm going to try and move him in with his girlfriend to see if it fixes things.
Edit:
Alright, I moved out the guy who always seemed to have aging disabled whenever a new day rolled around. It's still happening with the others. Well, sort of. The main panel will say some of them are stuck at 5 days until aging up, but when I go in with Debug, it'll say 4 more days, since it's the day after. I'm so confused by this game sometimes...