RE: 7 mm ultra mag, good gun?
Do you reload? If not skip the RUM's!!!! If you do reload then the RUM would be an excellent long range stick. Like Ridgerunner I agree their is little need for a RUM if your not going to be shooting 500+ routinely.
As far as heat, shoot 3 shot groups let it cool, repeat. I do this with everything but varmit rigs and rimfires. No problems. IfI can't hold the muzzle with my bare hand it is too hot to shoot! Personally I like it to come down close to ambient before shooting, when i go to the range i take several guns so that I am not rushing and keeps me busy.
In regards to barrel life,fact the first shotbegins the erosion process how longuntil a new barrel isdepends on many factors- loads (moderate, hot or ragged edge), cleaning method or lack there of any cleaning,getting it real hot, etc. True the RUMs and other high capacity powder cartsdecrease the life but even the likes ofa factory RUM it will be years for most. Re-barrel shouldn't be a source of concern any way should you really like shooting it and burn through it quicker then most. IME itleads to performance gains (assuming you buy a good one). If your looking for cheaper andsimilar performance of the factory tubes finding good take off's isn't that difficult either.