Let’s try to understand all this in order to look at the object with open eyes.
Firstly, the dust on the matrix does not harm the matrix itself in any way – it generally only harms the resulting image, and even then not much. Finding it is quite simple – if you start to get annoyed by spots in the image in the same places, when using different lenses at different zoom positions, then it would be nice to clean it. If you don’t notice this dust, don’t even bother cleaning it – it’s either not there, or it’s just not critical for you, and therefore you don’t need to clean it, spit.
Secondly, dust on the matrix is not dust on the matrix at all. There is a low-frequency and infrared filter in front of the matrix, which collects this dust – in the last two years, in DSLRs, it is customary to make this filter with an antistatic coating and when turning it on or off (as well as changing the lens), shake it in hardware (the filter, not the matrix) in order to this dust fell off. We are not talking about the effectiveness of such systems now, but if it is present in the camera, it is still better than its absence.
Thirdly, if you do not change the lens on the camera and shoot only with a standard or “fifty kopeck”, the problem with dust will not affect you at all. For example, in more than three years of using the antediluvian Nikon D70, I cleaned the matrix only three times, although I like to change lenses, and there are a lot of them. Well, at the time the camera was launched into production, the office did not even think about the need to deal with dust, and therefore there is no antistatic coating and dust shaker in this device. Therefore, if you change lenses only from time to time, and not ten times a day, as professionals do, you are unlikely to clean the matrix like they do – usually once a month, since the matrix will get dirty much less often.
Fourth, remember that self-cleaning the matrix can do much more harm than good – scratching the filter or leaving stains on it (which are no better than dust) is very easy, with careless handling, which is typical for inexperienced users. Needless to say, the assurances of a professional, like “yes, I clean everything myself without any special problems” are an unrealizable and expensive dream for a beginner – professionals change devices much more often than amateurs, and for them this is a working tool that can break from time to time, and which they paid for a long time ago, and many enthusiasts buy DSLRs “for the last”, and the price of an error (relative, not absolute) is much higher.
Fifth, think ten times before getting inside the camera and rubbing the glass with something – it may be easier to give 2000 times in half a year (a year or two) than to risk an expensive electronic device. That is why we offer a slightly different option for cleaning the matrix, which does not involve direct contact with the photosensitive element of the device.