Last summer Customs told us, flying 135, that it was any conviction, misdemeanor or felony and no time limit in how far back they would/could go. As stated earlier, it was in direct response to US Customs procedures, and it seems to be getting more stringent by the day.
One guy had a minor shoplifting charge from over 10 years ago, they denied entry, we flew him back to the states where he rented a car and drove across the border instead. Another had a DUI from over 10 years ago, same thing happened to him, so don't bank on the 10 year plan.
Best of luck in whatever you decide to do.