After a year and a half, the fan started to hum like a low-quality Chinese imitation, which encouraged me to take it out, clean it, and lubricate it. In spite of all the claims that it is difficult to disassemble, I can state without excessive modesty that if you have the right tools and the right people helping you, it is not difficult to disassemble at all. However, precision and attention must take precedence above everything else. I greased two bearings on the electric motor that I was working on. Used multifunctional gear lubricant. It is substantial, therefore it ought to last for a very long time. Following the completion of the maintenance, the fan resumed its previously quiet mode of operation.