Dust delete data dilemma

Anyone got any ideas how often you need to update the dust delete data on a Canon eos 1d mark 3? For example you you update every time you change a lens?
Many thanks,

Pete

Depends on how dusty conditions are. Even if you don't update it, most of the dust will typically be dust that's previously been mapped. Of course, if you don't use DPP for post-processing RAW and don't shoot JPEG, there's no need to update it at all.

I don’t even use that function for the follow reason. With the shaker system much of the dust moves each time the camera is turned on and off. Sometimes spots disappear completely and sometimes they move a bit. The only stuff that stays put is the real sticky stuff. So, if I take a dust data shot, the next time I power cycle the camera some of that data will have been changed and i will be mapping out areas that are now dust free while leaving the new areas of dust unmapped.

I do what I have always done with any of the non-dust cleaning cameras; I take a quick pic of the sky and check the sensor for dust before any big event. If it’s real dirty or there is a large speak in a noticeable spot I’ll do a quick cleaning. If it’s just the small stuff and be pretty invisible below f/16 anyway, it’s clean enough for that day.