You're never wasting upload. You upload always things other people want.
No, I'm sorry but that's not true. First: my example, I upload files to people who delete them the next day (because the file is incomplete).
Second, if a file has hundreds of seeders, vs a file with just a few, for me to upload the one with lots of seeders is a waste of an upload.
Maybe I micromanage the upload more than others, but it happens pretty often, and I have to jump through hoops to get aMule to upload the more important files. The priority levels just aren't "strong" enough, very available files still get uploaded when a less available file should be.