it can go either way. if you have multiple nihil longswords or something to that effect, save one for a special fusion. if you're looking for a weapon to help you in tartarus, fuse it. but remember, normal weapons can be fused again and again.
It seems like if this gets put into a guide it should titled and based on...
"Weapon Fusion & General Weapon Usuage Stratagy"
the last part of it refering to information on the whole elements and atributes on wepaons thing and how certain weapons can prevent a nock down, etc.
Oh, and FYI, I've seen rather small FAQs get through before. So even if you had about 2 pages of info, as long as you use filler like a retarded logo out of letters or something, make updates from questions and ansers you've seen that relate to the topic, and in general BS so updates and organize everything to a section, it should make it to the list of FAQs.