I "wash" my line with a cloth with silicone shoe protector spayed on the rag. I keep the rag in a baggy in my fishing vest. I leave my lines on the reel and store them in my rod closet.
Salt water guys may have a different approach to deal with the effect of salt!
Depending on the water you fish and how much "gunk" is in the water and on the surface film, washing is done more or less frequently. On dirty water, I clean my lines after each outing.
Also, any given line, after more than 70 days (?) of use will need replacement, for me that means not more than 2 years on average. Sooner for the lines that I use from my boat since I invariably step on them more than I would like to admit..
Pete AKA Frenchcreek from Calgary