AP1 retainers crack when they've been run on the ragged edge too often, or mechanically over-revved Mileage does have an affect on them, but typically, they last a very long time. AP2 retainers are beefier than AP1 retainers, so as long as you don't mis-shift and tach it up to 12,000 rpm's or so, your retainers are good. I've never heard of our valves floating, even up over 9000 rpm. My redline is set at 9200, and I've seen it quite a few times. 74000 miles and not one floated valve.

 

If you were talking about a typical ford or chevy, then this might be true. However with our cars this is not a problem, and you will not need to do a thing.