If you have another controller, try to move the ap's to that and then make sure you have syslog, so you can filter on specific logs. Logging can help you also determine if its happening to certain ap's, how often and maybe any triggers before the crash. If some ap's do not crash at all, I have seen in the past where the image was corrupted in the ap and deleting that image and letting the ap pull the image back has fixed the issue. It really comes down to how much time to you have to play around and test, vs updating and hopefully improving the user experience. AP's crashing is a hard fail on the clients and that will cause poor user experience, so figure out how much time you plan on testing before you just decide to patch/upgrade they system.
You can do what @Leo Laohoo mentioned, but look at your syslog filters to see if these ap's crash multiple times a day. Gather more data to help you with your decision.
-Scott
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