Word token frequency estimates for adult speakers

[Bill Croft]

(apologies for cross-posting)

Are there any published (or unpublished) estimates of how many words 
a typical speaker is exposed to (produces and hears), per day, or per 
year, or even in a lifetime? I am aware of some token frequency 
estimates of exposure to language use by children acquiring language 
(though I don't have the references), but not for adults.

I will post any references I receive.

Thanks,
Bill Croft