Should I keep generic reference letters from my supervisors? As for reference letters, I have come across distinct policies.

Some recommend to only give a reference letter for a particular application - it might be tailored to the particular position which the applicant soughts for.

Other do not seem to have a problem with providing generic reference letters. I personally prefer this one, because it is clearly less work for all parties involved.

So, which kind of reference is appropiate to ask for from your supervisor? Which one is socially accepted? (I am a former student that needs a letter of reference from his former professor).
Let me answer the question in the title.


  Should I keep generic reference letters from my supervisors?


No.  You should not keep copies of reference letters, generic or otherwise.  Your supervisors should send whatever letters they write directly to the jobs to which you apply.  Those letters should never pass through your hands at all.

It's entirely up to your references what kind of letter to write.  You should always ask for strong letters individually tailored to each position you apply for, but there's no way to make anyone do that, or even to check whether they have.  Ultimately, you just have to trust the people you ask to do a good job, which implies that you should only ask people you trust to do a good job.