How durable are budget adjustable dumbbells?

Most budget adjustable dumbbells use cement filled plastic plates rather than cast iron, which makes them bulkier at the same weight but still functional. The adjustment mechanism is the weak point cheaper selectorized models may develop looseness or clicking after 1 2 years of heavy use. Spinlock models with threaded steel bars are essentially indestructible. Read reviews specifically about long term durability rather than just initial impressions.