After having a good flight today at a local castle ruin(https://www.youtube.com/watch?v=_WtqkxcQ5gk). I as always checked my quad over for any problems. All the usual things like loose screws, connections etc. When I got to my propellers I was horrified to find three small cracks near the hub on one of the propellers. This would almost certainly broke on the next flight and could have ended in a wreck.
I always do post flight checks but will now be extending them to pre/post checks. The blades that I use are the coloured plastic type and have never crashed or been in contact with anything whilst spinning, except for the odd fly/bee.
Strangely on my previous flight I did have a large Bee hit that same blade and the impact was hard enough for the camera to see and pick up the impact sound. (https://www.youtube.com/watch?v=OGXkZTazMKs) I did do my usual checks after that flight but did not spot any problems.
Remember 5 minutes spent checking the blades could save you $$££