I think with a rolling course it’s probably important that the gradient, gain & loss are the same for both the first half and the second half of the course.
In this video there’s a example drift test with around 200 ft elevation gain and loss over the hour. Because it’s a few of laps of the same route it works.
I live in a hilly location, I found a 2 Km section that’s relatively flat (6 meters gain/loss) and I run laps for the hour.
Personally I have found that knowing my AeT has been important for my training. I’d do one even though the training plan only calls for 30 minute runs. Prior to using HR drift tests I was underestimating my AeT.