And here I thought I was modernizing buying a 9 dollar diamond coated pocket stone instead just keeping an Arkansas stone in my pack
I think if you are going frame this as something to think about in emergency/survival setting then you need to contemplate other things beyond convex maintenance.
Are you using a high end very hard steel that requires special equipment in order to cut the into a very worn edge? If so, will the edge last the time you are potentially lost in the wilds without requiring massive repair? Who cares if the edge needs more effort to maintain if it's difficult to deform?
The other end of the spectrum is using a purposefully softer/more basic steel that requires more frequent maintenance but is more easily repairable.
Take for example, the traditional khukuri. This is something that may make some heads spin because not only do they generally wear a convex edge but they also, obviously, have a recurved blade shape.
These knives are used day in and day out in Nepal. They see more use in a week than most survival knives will in a lifetime. Traditionally, they are kept "sharp enough" using a steel aligning tool called a chakma. According to the late-great Uncle Bill Martino, common practice after heavy use is to hit the edge with a few licks from a file. Eventuality, the owner will take the blade back for refurbishing to the Kami (blacksmith). They'll probably do this for most of their lives until the edge has been worn down past the hardened edge.
My long point is that we really put a lot of effort into making things more difficult than they need to be. Maintaining a convex edge isn't an issue beyond a skill set. I'm not saying that a convex edge is superior to any other edge. I'm just saying that there is nothing overly difficult about the maintenance once you figure out how to free hand it.
Once again, I don't think anyone is wrong here. I freehand. It's the only way I know how to sharpen a knife. I've tried a couple of sharpening systems and I don't get the results that many of you do. I know this is 100% operator error on my part.
For my outdoor needs, I can get by with a small stone and a small piece of loaded leather to strop upon.