I was going to change my chain at around 10,000km as it was a bit too loose and I couldn't slide my dropouts back any further. Then I decided to try an experiment. I removed 2 links, slid the dropouts to their closest position and though I'd ride a couple of weeks on that to see if it was OK.
I'm coming up to 2000km on the shortened chain, and 12,000km since fitting it. It is well past 0.75, but works fine still at moment.
I plan to post pics of my toothless sprocket when I do change.
Chain is Connex 808.