I thought this might have been a hot topic but a search turned up nothing.

My 91 Formula has plastic outer bearings which I had not encountered before. Just a simple brake job in the works, low mileage car so no plans for new bearings. Are these a potential issue? I found a few Ford truck forums discussing them and most reported no long term problems while others discarded them outright.

 

No. All the plastic is, is a cage, to keep the rollers from touching. There is essentially zero force on them when operating. Many vehicles come equipped with such bearings, and make it from the showroom to the junkyard with them still intact. Many replacement bearings also come that way. Doesn't matter; metal cages aren't any "better" in any particular way.