Not getting your heat pump professionally cleaned can end up in serious health problems, will cost you more money for running your heat pump and will shorten the lifetime of your heat pump.
Over month dust and debris will collect in your heat pump components, mixed with condensing water and moist air during the cooling season this mixture is the perfect breeding ground for mould and bacteria to grow.
This article by CBC describes a case in which a family developed health issues because mould built up in their heat pump.