TM Tires

This is partially a rant, but includes some questions for the long time TM owners.
I just returned from a trip to Gettysburg, PA! Great camping destination if you haven't been! On to the rant: I had two blow outs on the trailer, one on the way to the campgraound and one on the way home. By looking at the tires I could not see any visible wear and tear, and both tires had very low mileage.
Then of course having to open the trailer (twice) to change tires along a busy interstate, was not my best travel experience.
So, what do folks do to keep the tires in good condition, especially when a trailer sits for several months?
What are some ways I can tell if the tires are aging, and ready to pop?
I hope that I am not asking something that has already been covered in another thread.
Thanks for any and all comments and suggestions!