Mithril, Yew, Emerald, and Ruby deposits should have a significantly longer respawn timer (in excess of 2 hours, I recommend 3 hours).
I think that's a bad idea; high end CNR is already balanced by the amount of time and danger players face when trying to gather them, and since there already is a max amount of times allowed enforced by the rules. Then I can only see an increase in the respawn time to hurt casual players, and benefit guilds and people with huge amounts of time to play.
We ask the community to limit any looping behavior through a small number of areas to sixty (60) minutes. We ask the community to limit any camping behavior in a single area to thirty (30) minutes. In the case of logging in, harvesting and logging out, we ask that you simply do not do this more than 3times in a row over a twenty-four (24) hour period.I can't see what difference it makes in regards to the rules if you use 6 hours or if you use 45 min's to use up the 3 times a in row over 24 hours. You'll end up with the same amount of CNR and the later allows the player with lesser time to maybe make the trip he would otherwise surely pass up on.
If the idea is to lessen the amount of high end CNR in the world, then I suggest a change of the rules instead and setting the max to 1 or 2 instead and keeping the respawn time.