On the latest Stern games like TMNT, you'll notice Stern has removed artwork around almost* all of the posts in the playfield and now you'll see a wood toned circle around the posts. The pooling you mentioned (it's really blistering) used to occur in the artwork under all the posts in the playfield. With no art under the posts, you won't get any pooling under them, so don't worry about that.

You might see a little pooling in all the areas that the stainless steel ball guides are fastened to the playfield, but it seems to be minor compared to the pooling that used the occur around the posts. Well, minor that is unless it chips off a small piece of the blistered art. Some people have loosened all the ball guide mounting points and have put tiny washers under them to lift them off the playfield surface. That's a lot of work, for something you'll probably never notice.

*ah, the asterisk: For whatever reason, it does not look like Stern removed the art under the TMNT outlane posts, so you'll probably see a little pooling there.

Bottom line, TMNT is a great game. Re-read Yelobird's post above and just do what he says. More fun, less worry.