Upper limits to morpheme length

[Everett, Daniel]

Please excuse the double-posting.

I haven't worked on this stuff for a while, so I will undoubtedly show my ignorance of some large body of research, but I was wondering (due to a question from a colleague) whether there is any work that tries to derive a maximum morpheme length (I wouldn't think this would be the way to address the issue, frankly, but I could be quite wrong). 

As the question was put to me: "It seems to me that almost all morphemes are quite short…probably not easy to find one with e.g. 12 phoneme segments.  The question is is there
anything in known phonological theories which predict this…or is it just assumed that morphemes can be of any length and that the reason there are
none of length e.g. 624, 578 is simply that they would be unlearnable?  The latter would be my ideal view, just as the reason that no one uses a sentence
of length 624,578 words has to do with practical performance limitations."

I know that there is work on "resizing theory" (Pycha 2008) and various other approaches linking morphology and metrical structure. But those approaches so far as I know offer no principled upper bound to morpheme length.

Any help would be appreciated.

Happy holidays to all,

Dan Everett