Perhaps those of you that clean your lines after each use are washing / rinsing with detergent i/o soap. Can't use detergent on fly lines, which by the way is the predominent cleaning product out there.
I just rinse in fresh water, or run lines through a wet cloth. I have about 3 dozen lines (Cortland, S.A., Rio) and all are like new. They range from brand new to 11 years old. I still have my orig line, which is Cortland's 444 I in a 10wt.