when you say 17" not sure what you are referring to. The 7900 can only print full 4 side borderless on roll paper, on sheet paper it can only print borderless on the sides. It supports borderless widths of 10, 13, 16, 17 and 24 inches. So if you were printing to a 17x22 inch sheet of paper, you couldn't get 4 8.5 x 11 sheets on it. The 17" would be fine, but you can't print the full 22".
If you have 17" roll paper, it would work. You could print a 17x11 sheet full borderless and cut it in half.
As far as the equipment, if you print a substantial amount of borderless printing, you can over saturate the small white sponges designed to catch the overspray and end up with some issues. Whether 30 calendars which sounds like it would involve about 180 pages would be a problem I can't say for sure, but I think it would be fine. You can exchange the sponge for one without ink on it pretty easily if it gets too saturated, I don't know if a replacement can be ordered.
In the 4900 they designed this as a replaceable part (borderless maintenance tank) because there are a fair number of users printing borderless prints (i have several portrait studios using the 4900's).