A small file buffer size stresses the harddisk needlessly. I would also prefer a free scaling.
Wrong.
Wrong.
OK, nothing to see here, moving on.
amule is an application which has its focus on data exchange. Thats why amule's access to data is not comparable with usual application's data access. And that is why data caching is part of amule and that is why data caching is useful and important. Caching can be the job of the OS and in most cases the OS does some optimizings for data flow. But it is not necessarily sufficient and optimal.
Did you care to check the facts first? No offense, but you seem completely clueless regarding how OS and disk actually works when it comes to file access. What you suggesting here is simply wrong.
Anyways the health of my harddisk is way more woth than a few MB's of transferred data.
considering the things i mentioned above, it has to do with each other.
Please, do a favor - check google about "harddisk MTBF" before starting such discussion. You will save lot of time, and will educate yourself about many things.