The VMK19 holds up pretty well if you change the brushes before they wear out completely. The previous "cheapie" motors from
Kleen-Rite were terrible - for me, the top bearing would usually fail before the original brushes wore out.
I didn't know about the Ametek Eternity until now, but I buy the Domel motors from Windtrax, and I haven't had one fail yet. They're about 50% more than the VMK19. The brushes last much longer - I could probably go 3 years but I change them all every two. It's well worth the extra cost, especially since they're higher volume AND higher suction than the VMK19, as well as slightly quieter.