I replaced the original AVON Speedmaster Mk II front tire that came on my G5 at 7100 miles. It still had about 1/16 inch of the grooves but I figured any rain at all would cause a problem so I replaced it with a Dunlop K70.
The new K70 now has a little over 3000 miles on it and is showing almost no wear at all.
As for the grooved AVON Speedmaster Mk II, I see nothing wrong with it but I don't "push" my bike hard. In fact I seldom "push" it at all preferring to keep my bike and my skin in unscratched condition.
The peg draggers and canyon carvers that hate the Speedmaster's and wear out K70's in 3000 miles probably have good reason for their dislike.
Speedmaster Mk II's are old style vintage tires that are made for motoring along the pike at restrained speeds just like most riders did back in 1955. They aren't designed for charging thru the twisties and drifting thru tarmac corners.