...for a while now. I'm not an admin or programmer, so all I'm going by is observation and people's blog entries on the subject.

That said:
When the increments all went by weeks rather than months, "x years, 52 weeks" was relatively common (since that's only 364 days) and went away in a day or two when the actual year end was reached . But months don't have that problem, and "12 months" seems to stay on, from my random check, until it gets to "(x+1) years, 1 week" or possibly "2 weeks". It does still list weeks if it's less than a month. I have the vague notion that I checked Dorothy's page seven or eight days after she mentioned "12 months" in a blog a while back and it hadn't changed yet, so one week may not be enough.

Eric