Quoted from TigerLaw:I think PDI or Invisiglass is necessary on every game. With a ten machine collection you should be careful before buying your first sheet . . . you'll end up with ten . . .
I had a friend over the other night, and I thought it was hilarious when he went to point to something in my Tron and didn't see the glass.
But unfortunately yes, Invisiglass is like crack. You will just want more of it.