It is something I do not do regularly enough, and so too regularly I get to moan about decreasing distance when casting, and floating lines beginning to sink.
The Moldy Chum site has two excellent videos from the makers of Rio fly lines on cleaning and ‘re-surfacing’ your lines to regain maximum performance and maximise line life. It is a job that takes very few minutes and your line will be much better for it.
While all lines need regular cleaning, Rio recommends after 2 or 3 fishing trips, and ‘re-finishing’ after 7 or 8 trips, those of us who fish the volcanic Central Plateau of New Zealand’s North Island should think about cleaning the line after each trip. Pumice and pumice sand is a proven line killer.