I have a wooden pole in my sitting room that's joined together and works fine. I'm not sure if you could do the same with a metal pole though. I'm on the lookout for a certain metal pole at the moment but haven't seen one yet that I like in my size (about 12ft). I have definitely seen expandable poles which might be what you want.
Except for short ones for single bedrooms, any poles (both wooden and metal) Ive ever put up have been joined.
Shorter poles should have 3 supports (left,right, centre) as standard so buying 2 together should give you enough supports with spacing them out as required. If wood, Id use a bit of wood glue with dowel for joining. It'll mean a bit of drilling into the pole but it should be easy enough.