>>Can a penultimatum be something that comes before an ultimatum?
:-) I really liked this one!
I checked its usage on http://scholar.google.com and found that it was being used pretty extensively. There was "penultimate pregnancy" referring to the pregnancy that preceeded this one. (Previous pregnancy wouldn't be accurate, since any pregancy before this one would be previous.) There were some heavy-duty papers on chemistry that referred to the "penultimate" this or that, which had an influence on the behavior of the last whats-it. So apparently this word is in pretty common use. It's even used correctly in hundreds of news articles.
Switch to the general web, though, and you see scads of pages using it as a higher form of "ultimate". Hmmmm... Do you use it, to feel smart? Or avoid it, because you ARE smart and don't want your listeners off in left field? Or do you reserve it for things you hope get picked up by Scholar.Google? :-)
Me, I'm not into elaborate nomenclature. To what purpose would I employ a voluminous expression, when a more diminutive one will suffice?
Dave