I've been running my HY7000 since October 2011. Jeremy at Coralvue replaced the impeller for me under warranty, because it seized so soon after being placed into service (one month).
I've come to the conclusion that since this pump doesn't draw a lot of power, it also doesn't have a lot of oomph to overpower a dirty impeller shaft. So I have to keep it clean...vinegar cleanup monthly for best reliability.
PS... I should also note that my return is downstream of the drip from my kalk reactor. I've moved the drip as far away from the pump as I can in my sump, but I still think its an issue. I also run an HY7000 on my skimmer in a different chamber, and in the last 8 months I've not had an issue with that pump.