I had a 6 spd. Suntour freewheel come apart while riding. The only explaination I can think of is that the lockring (the kind you need a pin spanner for) must have been loose. The small parts inside were strewn all over the place and not worth the trouble to find. The result was a long walk. So while these may last forever, it's not a bad idea to check the lockring every now and then. I didn't think to.

Fortunately someone bought the remaining large parts on eBay for $10. The sprockets were in good shape, and I hate to see useful things discarded. It's pretty cool that these freewheels can be taken apart and serviced.