I put a 4' section on either side of the evaporator and don't regret for one second spending the money for them. Well worth having something that won't rot rust or give out. I think putting them the whole length of the house will just turn into a dust/junk trap. You may end up with any and everything in it possibly plugging it up. Either way you go now's the time to do it right. My vote would be for the composite drains. No fun tearing up your hard work. Good luck,
Brian Eldredge
Mooncusser Maple
16x24 post and beam sugar shack
2x8 CDL maple pro Wes fab filter press
Lots of shiny stuff now I need some more trees