Yes, I agree with you. They generally last at least 6 yrs & can last up to 10 or more.
What went bad on it? Not charging anymore? Then a contributing factor here would be a weak battery or main connections. Bad batteries will kill Alternators... Bad Alternators can kill batteries.
If it failed due to bearings and squeals or seized up, a contributing factor could be a failing belt tensioner or belt was put on too tight.
If you are able to take a photo of the part # area or label, I can usually tell where it may have been purchased, especially if it came from a chain store. BTW, most places will have the option of rebuilt or New.