Hello 'radioactivegem',
Searching through all the listing/selling policies I cannot find anything that suggests putting
a "final opportunity" notation in the title would be prohibited. See for yourself:
http://pages.ebay.ca/help/sell/questions/what-rules-selling-items.html
There are all sorts of related links on the page you can click on to bone up on the dos and don'ts
of listings. It might be unwise to use too many of your title characters for this announcement, however.
People search for items by decriptive terms denoting what the item is. It is unlikely many will search for
all the words "last time this item will be listed". Most of your title should indicate what the item is, but I'm
sure you can insert a "Last Chance", or "Final Appearance", or some form of "Going Going Gone" in the title
and then in the listing state plainly and clearly that you will not relist the item again.
I've seen listings that said that in the description section, - that the item will not be relisted, or that the
winter stock will 'shelved' for the season, etc. So if you want to proclaim some version of "Last Time" or
"Final Listing" in your title, I did not find anything in the policies to discourage it.