Can a writer write too much?
No, but he can edit too little.
No writer ever writes too much. If you have ever been accused of writing too much, it means that you have been making your writings public too soon. (Like me.)
A writer can never write too much, learn too much, read too much, or edit too much. But you have to maintain a balance. You need to read more than you write, and learn more than you read (since just being around people can be a learning experience). So how does the editing fit in? It will be difficult to edit a three word sentence. You need to write at least a little more to begin editing.
Rule of thumb:
In all honesty, I am not doing that at all with my blog posts. I should at least try.
It is always so much easier to give good advice to others than it is to yourself.
But anyway, if somebody tells you that you are writing too much, what they are really saying is that you are editing too little.