About the XP loss over time...
To me, this kinda seems like overkill. I never want to go to kedge keep again. Ever. Not because I now have a neg10 there... but because I did about 80 AAs there. Rurho, Finster, Thizik... they did more than that, probably about 140. They never want to go back. For them, they're bored, tired, and frustrated with the zone, even though they know every in and out of the entire place. I don't need an *Old Area Penalty* to help me figure out I've been to a zone too long.
Currently, my favorite zone in the game is highkeep. I've been there since level 65 with 40 AAs, and I'm still going there at 65 with 250 AAs. I started out there with around 4200 base mana, and our group would wipe to 2nd level stuff quite often, like the kitchen hands. After a while, we were pretty good at the 4th floor, doing Royals and the High Priest... This was around 150 AAs for me. Now, we're doing High Priest and Chancellor with less than optimal groups, and with a good group, we're smacking around the basement.
It seems wierd that the Xp bonus is reset at certain levels, but not at certain AA levels, when there is just as big of a range (or bigger) in zones like highkeep or first ruins.