When you get older, that speed as a steady pace would be harder to maintain, requiring a pace of 20 or so, with the average at the end being 18-19 or so. I can no longer maintain that and do not try, I ride over 2000 miles a year as well as other fitness activities. When I was in my 40’s and racing as a beginner I could do 40 miles in 2 hrs. No longer. Such is getting old.

In my experience, gravel and dirt road riding is slower than asphalt and I would be surprised if that’s not a typical experience.. Thus my question as to how hard and fast the OP expects to be riding where deep aero wheels would be beneficial for the aerodynamic advantage. I don’t think they are, but perhaps the OP is much younger and fitter, possibly races, can’t say. When I was facing and doing triathlon team races, I recall the general consensus at the time was an aero bar had less benefit at speeds less than 20 or so. That thought carried over to any aero gear. Possibly the thought process has changed, but thus question what kind of speeds the OP can maintain and will deep aero wheels really provide any advantage.