The three that have failed on me were due to the diaphragm being worn out and leaking. A majority of the cases I see online are about leaking, not clogging. This is a historical problem with diaphragms. of which I've been using for over 20 years and why LFS's used to do a good business in replacements.
They last a couple years, not bad for $20. All peristaltic and diaphragm pumps will have failure due to how they work. One has a moving rubber part and the other crushes and rolls over tubing. Both will leak at some point. The trick is knowing when they are on their way out
I'm running two Aqualifters right now and i feel safe