I did end up throwing my erasable pens away and am now using a fabric marking pencil. I am hand quilting and it's working fine for me; the white pencil comes off easier than the erasable "ink" did. Although just water alone is not enough ... I have to scrub a bit with a sponge, there's very little scrubbing involved and it's doing no noticeable harm. I used to have to scrub the erasable ink also and it didn't come off nearly as well as the pencil does. I have a basket full of bar soap slivers I could use as markers, but am not very keen on attempting to wipe soap marks off with a wet sponge and it could be years before the quilt is completed and laundered.
If the erasable pens "erase" for you, as a longarmer, then I agree that keeping working pens available is the best way to go.