In the "making of" book (I can't remember it's name), there are memos from the technical consultants saying that Voyager's top speed of warp 9.975 is "too fast", and would get them across the galaxy too soon. Then again, warp speed in Trek has never ever been consistant - the TOS Enterprise reached the rim of the galaxy in the first episode, in STV they go from Earth to the centre of the galaxy in hours, a few TOS episodes make random speed/distance claims, the NX-01 reached Rigel and then Kronos in days at warp 5 etc. Star Trek moves at "speed of plot".
Oh, and downloading episodes is illegal. Buy the DVD's like the rest of us