For myself, I considered myself in maintenance when I hit my original goal of 180, 10 percent body fat years ago. I'm at 165-155 now (most BMI charts say I could go as low at 130ish), but the extra weight I lost is just gravy. What mattered to me was not being obese.
Besides that, honestly the easiest way to make yourself crazy is the idea that maintenance equals one number and one number only. As many stated, variations happen for all sorts of reasons, and unless you get a huge upswing one way or another it's better to monitor over the long terms -- weeks at a time.
It's another example of how the maintenance mindset differs substantially from a weight loss one.
Once you get used to your body's phases, it's easier to set your own "maintenance range" (a little over and a little under) and only worry about fine-tuning things once you hit either extreme.
This gives you breathing room to focus on everything else while still managing your weight -- without it managing you.