by Antistone
Assuming you are referring to[o]Permanent Supply Center stickers (rather than, e.g. the stickers that go on the board in the circular slots near your max supplies track)[/o]
The maximum you can get over the course of the whole game is
[o]6[/o]
Obtained from:
[o]3 at the end of February, 3 at the end of May[/o]