Mine are indoor piggies and I have noticed the same thing. I even made a post about it a few weeks ago the same as you did.
I switched from using newspaper to carefresh bedding in the kitchen area of their cage. I like the change, the carefresh absorbs much quicker than the newspaper.
I also started putting cotton towels on their fleecy pet beds. I realized, the beds were not wicking the wee away from them and they were just sitting in it.
They still have a day, or two days in a row, here and there where they have much more wet bottoms than normal (actually normally they are dry, so when they are wet, it is really noticable...like WET!). I think it may be correlated with their 'time', because Penny sprays Honey quite a bit with wee whenever Honey gets frisky around her (they are both girls). She sprays her right in the face. I've started trying to keep track of the 'time' and the wet bottoms to see if they happen at the same time. My girls are on different cycles...they each come into their time about every 15-16 days, and are almost exactly off by a week from each other (they are about 7 months old, so quite hormonal). I always know when Honey has her 'time' because she rumble struts like a crazy pig (and funny, this is the only time she ever popcorns...rumble...pop....rumble....pop) while my other piggie, the subordinate one, it is harder to tell her 'time', she doesn't give many signals.
Maybe someone else has seen the same correlation between the girls 'time' and wet bottoms? I think the spraying has something to do with it.
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