Dutchman, you certainly must be nearing a record for non-useful responses.
I do not have any exerience with (brass) donut problems, so maybe I am not the guy who can tell you best. But, until that guy comes on here with a helpful answer, I will offer some thoughts.
First, annealing will not affect your ability to deal with the donuts, if that was part of your question.
Also, I have shot Federal .270 brass over a dozen times without having donut problems, so I certainly would not EXPECT donut problems with Lapua brass after 4 firings if everything is set-up approximately right.
As you seem to know, the donut is a thickening of the brass IN THE NECK just above the shoulder. When you expand a case neck with a button expander, that will tend to put the extra metal on the OUTSIDE of the case neck. So, a caliper should be able to show you if it is there and, if so, how thick it is. If there is a little and it does not affect chambering, you are probably fine. Some may argue that the donut might become so thick so as to leave so little clearance in the chamber that it will raise pressure by not releasing the bullet easily enough. Of course, that is theoretically possible, but not very likely. If the bullet is not seated as deeply as the donut's location, then it isn't an issue at all. Otherwise, looking for a few thousandths clearance between YOUR chamber and YOUR loaded case necks should be basis for determining if you need to do something.
Some will argue that the donuts will not be completely uniform in thickness, so the concentricity of your loads will be off and that will affect accuracy. You can check for that too, although it requires some fancy equipment.
If you do find that you have donuts that need attention, I am told that the proper way to do it is to size the neck without expanding and then ream the necks. That is the only way to get all of the donut clear through the junction with the shoulder. I have not done that, but it seems to me that it would require some attention to what diameter you sized the neck to (probably with a neck-sizing bushing die) and the diameter you use for the reamer. Of course, it is necessary to use a rig that centers the reamer in the OUTSIDE diameter of the neck. So, if you decide you really need to ream, I suggest you talk to a more experienced person than me.