Good first post, i am glad you searched to get a overall veiw ,but i think you are right and the post you are referring to has nothign to do with your problems.
I would get one of the alternators that died to be checked by a starter/alternator rebuild shop. They can give you an exact cause of its death. As it is not going to be windings rotor or brushes that fail in short time. It is going to be elctronics that fail ,so which one needs to be established as the root . Then you can trace it back for where it originates .
The battery may just be that the alternator cannot charge it and it dies from low volatage.
You almost need a volt meter to monitor the volatage when you drive to look for actual spike and dips to be able to start replicating the exact issue and resolve it.
You may have a splash sheild missing from under the car causing lots of water to wash the alternator frying it.