Mike,
As far as I know, no time limit was specified when PALANTH got the server space from the UMM. But then, you never know! As is the case with many of those types of services, lack of space always ends up being the big issue. For the time being, however, I don't think this is a problem. So, you are certainly welcome to upload material that is palaeoanthropologically pertinent (sensu PALANTH -- which, as you know, is rather broad), as long as it is clearly "kosher" with regards to copyright.
Jacques
Thanks for the clarification. What I'm currently thinking of is having the draft copy of my essay on my website for comment and then, providing you are interested afterwards, having the final finished copy both on my site and in palanth's archive.
Another thought of mine is what about providing links from that page to externally available .pdf journals articles which have been made freely available. An example of this would be McBrearty & Brook's December 2000 JHE article "The revolution that wasn't" on the origins of modern human behaviour :
http://www.hss.caltech.edu/~steve/files/mcbrearty.pdf ?