I had Wolverine Heating & Cooling do some preventative maintenance on my split system. They did a filter change and checked the refrigerant to make sure it was working properly. This was my first time but I would call them again. The cost was definitely reasonable and the technician was friendly and professional. I haven't called yet to ask more questions, but I would have liked to have more detailed information on the field report regarding the condition of the system and the longevity if they can predict it.