my last post didn't seem to take, oh well...
IMO, guardian is essentially a band-aid for the proprietor about to sell, they're just prolonging the enivetable switch to synthetic lanes. Again, in my opinion, unless Guardian has been improved in the last 10 years, any proprietor interested in keeping high average bowlers happy would think twice before applying guardian.
We had a house back in the '90's that used guardian on the heads. From what I recall it's essentially non-porus and the oil moves off of if very quickly. The heads were practially blown out by the 3rd game of league, you couldn't chase the shot left fast enough.
If sand got onto the lane (winter road sand not swept up), the ball would imbed the sand into the guardian causing air and lane oil to get underneath and make bubbles under it. It looked terrible and the shot on it was even worse.