Thanks for your replies, guys, much to chew over!
Keith: regarding the longevity issue, the sleeves I employ at the moment are archival and the same company makes portfolios, but unfortunately, that's the very "look" I'm keen to avoid. Oh, I think, from memory, it's Silverprint or something similar - need to check the last invoice.
You are right - it would be a relatively expensive buy, or, alternatively, a very nice gift to the right person. But then, so was producing calendars a high-level venture and that's why it turned out so profitable. I've always believed in chasing the big prize rather than the lesser: the chances are better simply because due to psychological self-imposed limitations fewer folks are chasing the big ones, and if you are going to be lucky, then you may as well be lucky well!
This really is sparking my juices because I have been pondering a couple of alternative shoots that would cost me nothing but some travel, which in a worst case scenario, would be reward enough.
Rob C