Interesting..I did not think of petroleum jelly as it can sometimes be itchy, but on the other hand I can see that it would not likely effect the foam as much as other lubricants. I think I would probably be OK so long as I am not stuffing them in and out 10 times per day though. I am probably more worried about the way that deeper insertion IEMs will tend to push ear wax inwards whereas the body naturally pushes it out.
That one downside that I see regarding insertion/removal frequency. With my GR07 I could remove them whenever, and insertion is not an issue. With the ER4 it requires a bit of time to get them in deeply without discomfort.