object/pack size x5 larger than a fresh clone?

Is there any reason why a fresh git clone has a object pack around 140MB but one that has been updated over the years has it over 700MB? (even with git gc --aggressive --prune=now and git fsck?)

$ du .git/objects/ 711364 .git/objects/pack

$ du *wine/.git/objects/pack 144692 git-wine/.git/objects/pack 144604 wine/.git/objects/pack

I had a problem with git fetch "Cannot obtain needed object" from wine's git repository (which seems to be something to do with http proxy, although AFAIK I don't have one) since about 2 weeks ago which obviously does not apply to anybody else as I would have heard from wine-devel.

Editing .git/config to switch from a http url to git url cure it... but in the course of investigating, I git clone fresh (there are only about 3 local changes so I could just git-format-patch them and move them)

http://source.winehq.org/git/wine.git git://source.winehq.org/git/wine.git

and I am a bit surprised that the new clones are so much smaller than the one I have been working on these last few years. (I have had the old one for at least 3-4 years).