I don't know why the early C4 alternator is such an issue, maybe the thing was poorly designed in the first place. In the past I had more trouble with the alternator than any other part on the car. If heat were the culprit, then the later C4 alternators would also suffer the same fate, so I don't think heat has anything to do with it, since all cars can get hot. BTW, the catalogs stopped selling the underhood air extractors years ago, I guess because they didn't work.
Anyway, it would save a lot of hassle if you buy the best alternator you can find or go to an alternator shop. If you buy a rebuilt from a chain store, don't be surprised if it only lasts a few months, they are notorious for falling apart. My experience with remanufactured has been only a little better. Every city has an alternator shop that can put in heavy-duty components into your alternator like bearings, brushes, rectifier bridge, and they stand behind their work because they have to. This is the route I took, I bought a cheapie alternator just for the housing, took it to an alternator shop, and had them beef it up. It's been a few years and I have had no alternator problems.