Bicycle Mechanics - Neccesary to re-do housing?

Right now I have taken off my old 8-speed shifters/brake levers and put on new Deore XT ones. I am not using any of the old cables, but should I use the old or new cable housing? The old housing is in perfect condition, but is a generic brand. The new housing is not cut to the right lengths, but is Deore XT quailty. Should I re-do all the housing? Will it make a difference?

Thanks in advance!

-Garrett

yeah, redo the housing...
gunk gets in there, slows up the shifting... makes it less smooth over time. so it's good to replace the cables and housing once in a while.

just cut the housing down to the same lengths as your orignials, and you'll be fine.

some ppl reccomend replacing the cables and housing once a year!! i think that's overkill, but im just makin the point that it's a good idea to change em

Thanks for the reply!

Only problem is that I have no idea what cables go where. I will just guess around, seeing what fits where. And also, I have only had my bike for 4 months, so should I wait to redo the housing until they really get gunked up? Or should I do it now before I loose all the housing? :p

-Garrett

oh 4 months??? i say just keep the current housing... and save the new ones for later, when you wanna tune up your bike later on