I have a 2001 Mazda MPV that we purchased almost 2 years ago. We have had about 3 alternators replaced in the last several months. NAPA alternators. Mechanics just keep replacing them and they keep going. Also, I think the battery has been replaced once. There was also a burning smell this time around that we didn't have the last two times this happened.
Not knowing where you live, there is atsb that says these are susceptible ot water ingestion. I'm sending a drawing along that shows anew cover for these to stop this. This may be your problem. Other than that the only thing ic an think of is make sure your battery terminals are clean and tight as well as on alternator and engine ground from battery.