How often to replace them depends on too many variables to give a definitive answer. Quality of shocks, roads traveled, etc. A good chassis or RV repair facility can usually provide good input on when a shock is due to be replaced. That being said, if you have OEM shocks on the coach, many changes in shocks technology have taken place since they were installed. So even if in good shape, worth checking into at least the Front/Steers replacement.
What kind? Road Kings have been used by many CC owners. Koni Adjustable SP3 were/are a good shock for CC's. The original Koni FSD's were not recommended by Koni for the front axle of our IFS coaches, as the were overwhelmed by the job. Koni does have a newer EVO 99 FSD like shock now, that is more robust, and is getting positive reviews.
Much will depend upon which of these shocks will fit your coach.
I've given this opinion before, but since the rear and tags do not seem to do as much for ride and feel of ride as the front/steers do - I've recommended Koni Adjustable SP3 shocks for those positions. Then on the Steers, I'd probably now look to see if the Koni EVO 99 are available to fit our front. I believe they would provide good control, while at the same time be a little less 'stiff/jarring/noticeable' over expansion joints, pot holes, etc. - then say the Road Kings.
I do have Road Kings on Steer/Drive/Tag. Koni Adjustable SP3 came out about 6 months after I chose the Road Kings. Or I would have put those on the Drive/Tag to save some money, and still get good shocks. My Road Kings are the smaller diameter generation 2 1/2" diameter vs the newer Road Kings I believe are 3"(? Not sure, but know they're larger diameter.). I have not proof of this, as I have not researched it closely, but I believe the larger diameter Road Kings have different valving, which allows for still great axle position control, but probably with less stiffness/jarring then my generation Road Kings. Perhaps someone who has had both can chime in on this...
Road King will work with you, so if you get a pair and decide you would like them re-valve to different settings, they will do this for you.
I'm very pleased with my Road King's, and they have done what I wanted them to do - improve handling quite noticeably. But, if I could retain that great handling, with a little less Front/Steer jarring over expansion joints, etc. - I'd be very pleased. I'm tempted to try a pair of the EVO 99's on the Front/Steers - to see how they help the ride... (Donations gladly accepted, as after all - I'd be doing this as a 'test' for all of us
!) (And while on the subject of testing, also feel free to send a few extra loose bills, as I understand that the Silver Oak 2011 is worthy of testing too... Yes, what I'll do for fell CC owners
!)
Best of luck to you, and please let us know what you do, and how you like ther results.
Smitty