On the plus side, it's super easy to inspect the tensioners by pulling off the engine right side cam cover. On some touring models you also have to remove the right hand pipe and footboard. You can lift the top tensioner shoe off the chain and look at it easily. For the other one you'll need an inspection mirror like a dental mirror. The problem appears as excessive wear and pitting in the plastic shoe material. Some speculate prolonged idling with the bile on the sidestand deprives the cam chain of oil and leads to earlier failures.
the cam bearing problems were on the first two years of the new twin cam motor 99-2001 models and do not affect later model bikes. The tensioner problem surfaced with the late 2003 to early 2006's. There's some pretty good info going around that the problem was traced back to the dies used to stamp the chain links out leaving burrs on some links. As late as 2011, my local dealer was replacing the infrequent failures on low mileage bikes and covering the labor for doing so.
Unfortunately, going gear drive is not always an option if there is excessive crank runout aggravated by doing away with one of the two tapered roller bearing on one side of the crank starting with the 2003's. and using a roller bearing in it's place. If you are considering gear drive cams, sites like SS and Andrews have instructions for measuring run-out and different part numbers for cams with gear sizes to match what you measure on your motor. Harley themselves came out with a new redesigned cam bearing plate incorporating new hydraulic tensioners along with a high flow oil pump that is easy to retrofit to older bikes.
I inspect mine annually, 45K miles and no problems so far on 2005. For bikes with the problem, it is pretty evident it exists at 10-15K miles by the condition of the tensioner shoes. BTW, the Twin Cam motor went to chain drive to pass EPA noise drive by specs.
The nice thing about HD is they are like Chevrolets, parts are everywhere from multiple sources.