It's hard to guess, but just judging from anecdotal evidence, the risk on condensers is very low—probably a fraction of a percent with any real problems—while the risk on ribbons is very high... like 80%. Fortunately, they are shipping them with spare ribbons this time.
The sum total of problems I had with my condensers (I bought four last round---two LDCs tube condensers, two 310s) was pulling it out of the box and finding a screw on my living room floor abd hearing something sliding around inside the power supply. One of the screws that was supposed to hold one of the XLR connectors in place had lost its nut (and maybe washer, I forget). Somebody hadn't tightened a screw enough. No big. I would expect the condensers to have almost no failures of consequence, though I'd expect probably one out of fifty or thereabouts to have some relatively minor problem like that one.
The ribbons... I bought six---two each of the lollipop, the Royer look-alike, and the double ribbon. Of the six, all four of the single ribbons arrived with a sagging ribbon, at least a couple of those were badly stretched with the first several folds on each end completely straightened. That suggests that something physically stretched the ribbon violently during the manufacturing process. I think you could mic up John Bonham's bass drum with the ribbon mic in the blowhole and you'd get less ribbon damage.
The big difference with the double ribbons is that the plastic cage protects the ribbon from air blasts, though I can't imagine how many PSI it would take to do that much damage through the cage f the ACM-3....
Anyway, the bottom line is that if you order a single ribbon, expect to disassemble it and install the replacement ribbon as soon as you get the thing. Anything less is probably not going to yield good results unless they fix whatever severe process problem caused the radically stretched ribbons.
