I guess it depends on why you're boycotting. If the company does something you don't like, and an organized boycott attempts to change that, and it works, then the organized boycott will likely end. Some corporate decisions can be reversed, and some can't. I still hold a grudge against Starbucks for destroying the Coffee Connection (a local chain), even though that was more than twenty years ago and I still avoid them. That's an easy choice, though, because their coffee isn't really that good and there's plenty of alternatives.
It becomes more difficult as corporate power becomes increasingly concentrated and the government loses its will to fight monopolies. Your choices are diminished. Do you shop at Amazon because you love Amazon or because it's the only choice? Personally, I try to shop elsewhere as much as possible. Amazon doesn't have to do anything particularly evil (leaving aside for the moment their questionable labor practices, and other problems), but resisting monopoly power is itself a viable goal.