I watched the original series when it started in England in the early 90's, It started to go a bit south after the writing duo of Rob Grant and Doug Naylor split their patnership. Season 7 was the first to be written with only Doug Naylor and other writers doing the scripts.
It was during this season that Rimmer left the show the first time like geegad said and i agree with him , that this is where it lost.......it. It was still watchable but just didn't have IT anymore
I do have to recommend the Book though, Red Dwarf, Omnibus Edition, Better than life. Very funny book ;D, a must for any Red Dwarf fans
Gag