I've used a few. I have yet to see one deteriorate with age, although it's only been a few years now (not near my notes - the oldest is the one in the studio, which I
think was three or more years ago).
I'm sure they eventually
do wear out, but all indications are that they'll last at least as long as the 1046s, so I've got a few years to go yet.
You're right that they're pricey - especially in cooling per $ - but they're quiet. They
do vibrate, though - like the 1046 and 1048 (more than the bigger Eheims as there's less mass to resist being moved). I've sometimes thought that the real answer to pump vibration was to bolt them solidly to something like a 15lb scuba weight. I've turned into a warm-water diver, though, and never seem to have weights on hand... (Not that I
ever thought ice diving was fun, or even a good idea
)