If your 7-08 is a hunting, then 3 shot groups will probably tell you all you need to know anyhow. I mean, in what situation would you fire over three shots in a relatively short period of time?
MANY times I have dumped all five rounds as quick as I could acquire the target, on those darned hogs of course.....shoot them till your empty, then reload, and go find some more.
To the OP, I generally use the inside of my wrist, right behind my palm, laid on the barrel just ahead of the chamber to check the temp when testing out loads. I had an old fellow who shot BR show me that years ago. If you can hold your wrist there for a 15 count, then your usually good to go. Once it gets to hot to do so let it cool down. I have a few rifles that I can shoot up close to 10 rounds with a minute or so wait between shots, and another few that it only takes two shots to get there. Many different factors involved, as these are all different barrels and different calibers. The powder choice is most often the culprit, but not always.
Also as mentioned the temp of your chamber can effect the next round shot, if it is pretty warm. Interesting test is to take one, or a couple, of small cheap styrofoam coolers. Use one of the gel type ice packs, for a cool weather test, and one of the large chemical type hand warmers for a warm weather test. Lay a hand towel over the ice packs and the hand warmers then a couple of rounds on top of the rag. Let them get either cool or warm and shoot them against your ambient temp ammo. Be very careful if your loads are on the top end, as this has bumped a few of my loads up into the sticky extraction area.
It will however show you real quick if you have a load that will vary much depending on the temp. You also need to be sure you chamber is at ambient temp to test as well. I usually do my development in the early spring, while it is still fairly cool. The above test is cheap and easy to repeat, so I use it if I work up a load that might be questionable. It only takes one of the bigger sized hand warmers to get the temp up to a good summer time heat index of around 100 degrees, and any cheap thermometer, will work as a indicator letting you know how long to let your bullets lay on the rag.
It might sound a bit overboard, but I have had great grouping loads, go to sorry grouping loads with only a 20 degree temp change. It has had me starting to wonder about the rifle when it was the load all along.