If you start a new ez-board community I suggest beginning with just one general forum, or possibly two with the second one for advertising. When a forum gets a lot of traffic it makes sense to split it into a number of specialized topics for convenience, but forums don't start out with a lot of traffic and splitting maybe three posts per day among twenty different forums does not make it more convenient to follow.
Much the same applies to the idea of splitting off a watch forum here at Bladeforums. The question is not whether to discuss watches here; we do that. The question is whether to split off that discussion from the rest of Gadgets & Gear. Probably not a good idea at this point IMHO; threads stay on the front page of this forum long enough to make it easy to find the watch threads.
People tend to assume if a forum is split into specialized topics that will suddenly create more posts on the subject that interests them. In my experience that doesn't happen; in fact traffic usually goes down when a small forum gets split and sometimes it dies completely. A forum has to get new posts frequently to keep people coming to it; if people keep coming and finding nothing new they stop coming as often, and if they don't come often they are more likely to stop coming at all.
A thread format like vBulletin or ez-board is much more convenient, but it has a cost, one way or another -- either you have to raise money to start it and more money to keep it going, or you have to put up with the ads at a free ez-board forum. It would be great to have a watch forum with a format like Bladeforums and a membership like TimeZone, but ... well, if somebody had some money to invest he could start a forum and try to lure the watch experts to it.... Failing that, starting a free ez-board and trying to lure the watch experts to that ... might work; they might be more willing to put up with the popup ads than to continue putting up with the inconvenient software at TimeZone ... they might prefer that enough to make the change ... if you start an ez-board forum I'll come to it; I can promise you that. Whether anyone else will, though ... well, there's only one way to find out.