I clean mine about every 3-4 months, it's a bit of a chore as I have to clean the kids bedroom and they are usually a tip and you are looking at 4 hours to go all through but I usually do it all in one go as I don't feel like doing 1 room at a time, I have an aniline suite so that gets cleaned and colour balmed and that's another time consuming job, I clean and protect it every 3-4 months and a balm once a year ish, we live in an older house and you tend to get a more dusty feel to it, before we lived in a new build and that kept clean far easier.
Shaun