I hate to be vague here but there are several factors that may play in to how often you need this...what's in the water you are using and how much you use the system.
There is a lot less organic matter and minerals in RO filtered water, basically none in distilled water so it will take longer for deposits and bacteria to build up in the system. Don't need to clean as often.
If you don't need to use the humidifier all that often the water will sit longer at a time and probably require more frequent cleaning than if you are running large amounts of water through the system every day.
If your water is fairly hard and you see mineral deposits building up pretty quickly you will need to clean the system more often to get rid of it.
With my RO filtered water I think I tend to clean the system about once a month. If I don't use it for part of the year I empty it out and clean it before letting it sit idle.
I have a baby Jackson I run my humidifier 24/7 - it's a cheap one I got at Target -I put a tube out the top it has a tube that directs it over one corner of the cage but the humidifier sits outside and is aimed at the area i am trying to keep cool and more humid the corner of the cage away from the basking light.
I do the top part when I add water - every day or twice a day . The bottom about every 3 or 4 days with the tubes. I'm a newbie - so if someone who knows better tells you something different I would go with that- but in general I would say the more you disinfect the better- I just use a antibacterial dish soap and rinse real well- when I do the tubes i soak them.