I have been negotiating with about 10 of them this last 6 months. They are generally offering a per rod amount, and as you said, permanent easement of 30 feet. Some start with a bigger permanent easement, but usually, the size doesn't have to be more than the 30 feet. Get a rental for the temporary easement and time limit it to about 4 months. There is a University Lands Rate Schedule on the University lands site, and it is a great place to start your pricing. Note that the university easements are for 10 years, but I really don't want to be policing that in increments of 10 years. On that same schedule, there is a "current" renewal amount, but who knows what that renewal amount will be in 10 years? I usually start with the schedule which is by pipe size, and add two rental periods to it to give a "permanent" easement FOR ONE PIPE. I insert a clause that if the pipe isn't use for 12 consecutive months, the easement reverts to me (or my heirs).
They will scream bloody murder, but i have been averaging $200/rod for the past several years in Reeves and Ward counties. A lot of these companies are not ICC carriers with rights of eminent domain, but be careful--there is a specific court that can grant the eminent domain much faster than you think. If the pipeline company wins, they have to deposit money in an escrow until it is all finally settled, but once they do that, they can start the process of digging.
More bothersome are the power transmission guys because they are almost all ICC and they want huge amounts of land to put big towers on (easements of 80 feet or more) and lots of voltage overhead. Because they can "eminent domain you", they aren't near as much fun to deal with.
Another ploy I had to deal with this month was a company that wanted to put a "temporary" water pipe on top of my land--they are lazy because there are lots of buried pipes all over the area, and didn't want to do the work. I stopped that quickly, and now after studying their proposed line, they have decided to look at another area and avoid me. that is my last problem with them--big hurry, push and pressure to sign their agreement and you spend the time and resources and they decide (without telling you) they have changed their minds.