Copy files between libraries by keeping versions

What I want to achive with SP 2010 Foundatoin is to copy one ore more files from a library to another one inside the same site on a regular time base. I have set up a simple workflow (my very first one, I am not familiar with designing workflows at all) which starts manually and copies all files from librayA to libraryB. This works fine so far, beside the fact that the files are versioned. The point is that fileA in libraryA has 2 minor versions like 0.2, the copied fileA to libraryB also shows 2 versoins 0.2 but unfortunatelly this is 2 times the last version only. So there is no difference between version 0.1 and 0.2 looking at the copied file in libraryB. Even the size is the same. This is not true for the original file in libraryA. This looks to me like abug. Either versions are not kept on copy or they should be real versions.

Any idea why this is as described? Isn't it possible to keep the versios roceeding this way? Is there any other way (not as an export via PowerShell with -keepversions switch) to achive this?

Actually I'd like to run this workflow automatically on libraryA which let's asy is set to keep 20 major versions and no minor ones before the 21th version gets deleted. this way I actually can keep all versions of a file in an archive but not booting the original working file.