I remembered reading this again when I saw the discussion on the "complete bond" by Rand al'Thor and esp fionwe1987's comment "So the Asha'man will get their 'moon cycles' aligned with the Aes Sedai? ".

Anyway, I can't find the complete quote, but it was in the WH prologue where "Elayne mentions that she and Birgitte 'mirror' each other so much that even their menstruation cycles are in sync [WH: Prologue, Snow, 27]" (thnx to the FAQ). I think it was mentioned that Elayne's cycle shifted almost two weeks in order to align with Birgitte's.

I found this quite odd. Aligned? Does this imply that Birgitte experienced a menstrual cycle when she was in TAR? Remember that she was bonded the moment she was torn out of TAR. So there was not much time for her real body to experience a regular menstrual cycle that will need to align with Elayne's.
I find that a funny detail for all female heroes while spending eternity in TAR. Do they also need to eat? Or sleep? Where do they buy their tampons, or do they need to imagine having one in for a couple of days? And of course a clean one every now and then. (Sheepwool pads, I think it should be?)

Personally I think this was RJ's attempt to put some realism into the female-female bond (let's-invent-something-that-makes-this-bond-special-and-this-is-what's-normal-for-women), that backfired IMO b/c it was not thought through to much.

But then again maybe the Heroes DO need to eat and sleep. Who knows?