I bought a pair of Shimano PDA600 SPD pedals along with a pair of cheap-ish Garneau Terra MTB shoes in early 2012.
I wear them for my daily commute (approx. 18 Km) and semi-regular long distance rides. I also walk on the street with them - to the office, pub, etc...not very far.
The cleats when new have right-angled edges, but now they have been "worn"/"smoothed" into more curved edges.
To use they "feel" a little bit loose, but sometimes they feel quite sticky (hard to remove my foot from the pedal), so I'm not sure.
On other pedals, I've changed cleats every few years, but I rode a lot less.
Is there a recommended period of time (based on usage, etc) to change cleats on MTB shoes?
Also, is there any suggestions on how to increase the life of your cleats? (I guess one would be don't walk on the street!)