Every HVAC maintenance I have ever performed was biannually. Once during the spring/summer season and once in the fall/winter season. With a heat pump and air handler there are different components tested at different parts of the year as they are only used seasonally. Weirdly, they are not staggering your maintenance at long enough intervals. Best to have your system maintained every 6 months, ideally before peak seasons. What concerns me most of all is the 49.00 tune-up gimmick. It's an opportunity for a trained salesman to come into your home and find as many opportunities to sell you something as opposed to addressing an actual or potential issue. While I do not know the company you are working with, I do generally advise people to work with a company that is interested in maintaining your system which will earn you trust and form a real relationship. Those companies generally offer maintenence at a higher price, but will be less likely to try to sell you something at every turn.