It's interesting you were able to hit the White Tanks repeater from Rim Rd. I'm up in that area pretty often. I like camping around the Knoll Lake area. We do a lot of off roading all around Lake Pleasant and north of the lake, so having a dependable repeater was important to myself and the group I go out with.
This is all new to me. I've only had my GMRS license for a week. I added a few repeaters to my HT in areas I like to off road. I'm in AZ and we have some repeaters that are on very high mountain peaks. I joined a couple people in a conversation a couple days ago and they said I was coming through perfect at 40 miles away. They come through on my HT as clear as a phone. Several repeaters in AZ advertise 100+ miles and a couple can go much further than that from what I'm told.