I'm going to start to change mine regularly, after I get the drone back from repairs. Last weekend I experienced a crash due to both rear props breaking at the hub and departing company.
The drone is only 6 months old, and I have only ever hit my thumb (when trying to catch it on landing) and the grass when landing on the lawn with the props.
I'll do it regularly from now on as I was lucky that the flight they let go on was just around our yard draining the batteries, I'm usually flying it from our boat filming our boating and fishing stuff. I'll also always use the rescue float and wetsuit I got from Phantomrain for all flights now.