Actually base grinds are MOST dependent on base edge angle!
If your base edge bevel is over 1 degree you need a grind and need to reset the base edge to 1 (or less).
I don't care what the structure looks like.
Base being concave is also not a reason to grind unless they are concave base edge to base edge.
As long as the base is flat 10mm in from each edge with concavity only in the middle they will ski fine!
Convex is an entirely different kettle of fish. If they are convex, I would seriously have a shop look at them and see if they should be replaced on warranty. This is often caused by a defective pressing process when the skis were built.
You should NOT be sharpening the base edge for routine maintenance. This will only quickly increase your base edge bevel and require a base grind. All edge maintenance should be done on the side edge only!