I, for one, am in favor of the gear drive cams. S&S now offers them with built-in compression releases in case you decide to cam-up a little.
At the beginning of the season, I replaced my tensioners, and while I had it opened up, I put in a fueling high-flow oil pump and heavy-duty cam plate. I was going to do the gear drives then but I hadn't decided if I was going to bump up the HP or just do a 10 over clean-up of my cylinders. I have opted for the clean-up since, with my riding style, I really don't need any performance increase.
We have installed the gear drives, with and without compression releases, on twenty-some bikes for customers. All of the comments have been positive except for being able to hear them and that seems to decrease over time as the gears wear in.
If you just want to replace the tensioners, there doesn't seem to be any consistant data on how long they last. Comments seem to be between 30 and 60K.
As stated above, there are a number of posts about the tensioners, even some detailing how to replace them.
Hope this helps, and welcome to the forum.