I go sometimes weeks but once the soap scum starts building up I usually think I need to clean this. Then after cleaning, it looks like a brand new razor.
Every time I clean my razor and get it looking new, I have that "ooh shiny" feeling.
I clean after every use. I keep all my shaving gear in a special box so like to keep it all nice and tidy. It also means I don't get moaned at for leaving a mess in the bathroom.
I soak my razors in baby oil after each use...I can get as many as 10-12 shaves out of a DE razor depending on which brand.
Be it my DE or my straight razor, I completely disassemble them after each use, lay them on and under wash cloths and the use a hair drier, set on cool to dry them. I've forgotten how long ago I changed blades but I remember I was buying cards requesting people not be my Valentine and listing consequences if they did.
Great idea about the baby oil, have to try that.
When wet shaving i clean the shaver every time.