It depends on what you are watching usually. The more movies you watch, the more likely it is to happen.
The studios may change their codecs slightly, requiring you to update the player to correctly decode it. I've run into this with Oppo a few times, but they've always released an update to correct it. On my PS3, I have run into a number of discs that had issues, but they also regularly release updates to fix this. The PS3 more or less forces you to update to access online features, but I tend to go ahead and update it. I've updated the firmware on my Panasonics, even though I never ran into discs that wouldn't play.