If the teeth look like this (see middle chainring) you have left it too late. (not my bike I will add!)
But seriously, I take the 0.75% and 1% thing with a pinch of salt. There is very little difference between the 2 on chain tools and one chain tool can say you are over 1% and another will say you have not reached 0.75% stretch... My current one is an over-estimator, so when the chain tool fits at 1%, the chain is replaced and after the 2nd or 3rd new chain, the cassette or chain rings are replaced as needed.
(The photo above is my OH's bike. He does not clean the chain often, was on his 3rd chain as it was (though only 2,000 miles covered) and I had taken matters in to my own hands to get his bike operational again after he complained his chain was slipping

and I was fed up of the noise his rear hub was making when we were out cycling together!)