Originally Posted by
Koyote
And that probably happens pretty quickly on a $2 derailleur.
You can think of them as disposable. If it costs $2.25 every 6 months, it is not a problem.
Where I am there is a lot of mud and dust. Mud can come off the front wheel, onto the chain, and onto the jockey wheels. Dust sticks to anything with oil on it. If I used aluminum jockey wheels with ball bearings, I am sure some dust and mud would find its way into the bearings. Disposable parts are idea in this situation.
Most likely this derailleur will never break. It is cheap because it is old style, and people selling modern bikes don't put old style derailleurs on them. You won't find a stronger derailleur.
Plastic jockey wheels in any derailleur will also wear out fast, compared to aluminum jockey wheels with ball bearings.