Hi all,
Although it's good practice to maintain clean optics, it's not always possible to have them spotless and not a good idea to continually clean them. In my opinion, once a year would be extreme for internal camera optics, though using a blower only can be done as often as you want.
It doesn't usually go over well for some reason
, but the practise of flat fielding exists valid reasons and the removal of inevitable dust spots from images is one of them.
Just a suggestion!