Yeah- I had tried to respond last night, but could not...
The fine art world is an area that I know very little about, so this is not a loaded question, but is it not possible to produce limited edition prints/series for galleries and sell different material via websites etc. in unlimited quantities?
Or if you really want to re-use the same material, could you not make the limited edition prints somehow more sexy (e.g. different size, different toning, different paper) and keep the unlimited editions to a still solid, but less exciting configuration?
To your first question: Typically galleries will not allow selling of non-limited edition prints either through the gallery itself, or by a contracted artist on his own (website, direct sales, etc.). The reason is that the selling of unlimited prints decreases the overall value of the individual pieces. If a gallery knows that you sell or have sold large quantities of uneditioned prints, you become much less 'valuable' to them. If there are 100's of a certain image floating around, why would someone want to pay high prices asked by galleries? If on the other hand you are asking weather one could sell image A in limited editions through a gallery and image B on his own in unlimited quantities... that's a bit of a grey area. Technically it would depend much on the arrangements you have with particular gallery. Some galleries ask for no-competition clauses which grants them full rights to sell all of the artist's work through the gallery at the agreed upon commission. Usually, this is only for those higher end galleries that will get a great deal of business and interest from a high profile artist. Many do not ask this however, and in this case I suppose it would be possible though perhaps frowned upon.
To the second question: Typically numbered editions will correspond to a certain number of prints made at that size, though not always. Larger sizes tend to have smaller editions, thus (theoretically) further increasing their value. As far as simply changing one small aspect about the photo, and then re-issuing a 'new' edition... again, I would say that's just a bit deceiving... Editioning is traditionally reserved for completed pieces... there is an A/P (artist proof) for works that are not complete, or may undergo such changes that you mentioned (toning, paper changes, etc.). These are sort of test runs so that the artist may proof how it will look, and decide on a final presentation of the image before beginning the full edition of that particular piece.
In the end, I'd say it all comes down the the artist himself making the decision. Some artists do not edition. Some are very strict and offer their work in small limited editions. Then there are people who fall anywhere in between. But, if you are going to edition, do so properly. Do not try and trick people that you are offering a limited edition all the while assuming that you will simply re-print at a later date if the edition is exhausted. Choose an edition size that is not excessive (1/10000), yet will allow you to make a decent return on said image.
Personally, I edition every print I make. I usually do small editions, at most 50 or 100. My reasons for doing this- some mentioned above, galleries, etc. Also, I don't want to be selling the same image over and over again my whole life. If I sell 50 or a 100 prints of one image, I'm quite satisfied. Plus, if I am selling the same images I made 5 years ago, then I'm not improving my craft... so it just pushes me to constantly produce new and better work than before...
-Jason