SPD's and increasing float

I've got new Shimano CX9 mtb shoes, new SPD cleats, and older Shimano SPD pedals - probably 10 yrs old, but with not that many miles on them.  My left cleat has a few degrees of float but my right cleat seems to have double that amount.  What's going on here?  Do SPD pedals wear out after only a few thousand miles?

Posted Sep 09 in the Components - Discussion and Reviews category

"Yes, the tightness of the cleat/pedal interface is subject to wear.  Personally, I find that brand new, the cleats have too much friction that prevents smooth float.  Then they break in, getting smoother in float but also slightly increasing in slop.  Over the next few thousand miles I gradually increase tension whenever I notice pulling out at a stoplight.  Eventually even at max tension, they're sloppy and loose and can't hold a sprint.  Then replace and start over. As for the asymmetry, I'd bet anything that you ride in a left-hand-drive country like the USA, and you tend to clip out with your right foot much more often than with the left.  Just swap cleats and they'll even out over time."

Thanks for your thoughts on this - that's what I assumed was going on, but I've been away from cycling for so long that I wasn't quite sure.  Yup, USA.  
EB