From my experience the touring bikes fail a lot earlier than any other. Ihave seen some completely gone @ 20k and some last as long as 40-45k miles. So if you have a touring model with 20k or more miles iwould definatley pop that cam cover and check. I just built the motor on my dyna with 37k- the primary tensioner was about 1/2 gone, but the rear maybe only had a few thousand miles left. I was going to go gear drive but already had cams, and did not want to spend any more $. I did put in a S.E. hybrid billet camplate and pump, that comes with the new hydraulic tensioners and new roller chain and sprockets for the front, but uses the old silent chain on the rear with a hydraulic tensioner. The new tensioners last a lot longer. ( havent had to change any yet and ive seen some bikes with over 80k miles )
Twin cams up to 2006 have spring loaded tensioners except 06 fxd. Anything 07 and later have hydraulic tensioners.