Ongoing dry skin, over a year of different treatments

Sylvie has had dry skin & quill loss (with growth) since I brought her home October 2008. She was born August 2008. This is a link to a bit of the back story on the dry skin: http://www.hedgehogcentral.com/forums/viewtopic.php?f=5&t=2675&st=0&sk=t&sd=a&start=10

In short, just before I got her she was treated with Revolution as her brother had mites, so she came to me with slightly dry skin.
Fall - I try adding flax & Olive Oil to her food, she loves the olive oil but no change. I don't add the olive oil any more.
Around January, she was treated again a for mites (there was dry skin but no evidence of mites, but treated to be safe) with Revolution, no change.
June - We add Sunshine Factor as a supplement to her diet, which she loves. & does seem to help a little, but no actual skin clearing. The vet did a skin scraping & thought it could be fungal so we treated her with Program Susp, no change. (above thread discussion)
Oct - With no change still and my having recently recovered from a yeast spot on my chin where I rest it on her cage, we thought it might be yeast. To cover bases as all the tests he was sending away were coming back negative she was prescribed Enrofloxacin & Hraconazole.
November, skin seems to be cleared up, quill loss is almost non existent.
Last night (Jan 2010) - I notice two big patched of dry skin on her rump again. The dry skin is so thick it almost looks like she's rubbed her bum in cotton balls and got the fibers all in her quills (she hasn't). Her nice gray skin can't be seen through the thick layer of white.
She hasn't (to my notice) started itching a bunch as she did this time last year.

Has anyone had experience with this? Provide some guidance? I don't want to keep giving her antibiotics as I'm afraid they'll weaken her natural immune system (think human superbugs) but I will if that's the only answer. The other thing I wonder is does she just have normal naturally dry skin & I'm fighting a loosing battle? As some pets or humans have Eczema, should I start looking at this as something to control over cure?

Edit: Fixing dates