A fresh rubber would usually last me a couple of weeks, minimum.
Some change their's every day.
Now as most my work is WFP they last for ages, but I also use several different sized squeegee's and always have done.
As you say though, now and then you end out getting a tiny 'nick' somewhere along the rubber, then you have to turn it to use the fresh side, or change it if both sides are worn.
What I find really annoying is when I have turned the rubber when side 'one' has served its function, and you turn it over, only to find that the nice new edge has an invisible 'nick' in it half way down
Usually when I am 10 miles from home and I've ran out of new squeegee rubbers in the car
Regards
Ian