Up in NJ, installed a Sears system in 1971 when we moved into our A/C-less home, never serviced in 28 years other than filter, then got a new Goodman system installed in 1999 with all the money we saved on check-ups. :) that too was never serviced in ~18 years other than filter ...... then moved out in Jan 2017. Only problem we ever had was the 220 junction box outside "broke." We did have a small condensate pump that did die a couple times over the years that drained into the laundry room sink. There was no pipe just some plastic tubing that never clogged. Of course it wasn't used as much as here but still ....... We had 10yr P&L warranty from dealer but never used it. It did not include "checkups."

Sunshine has changed from twice to once per year. If you feel uncomfortable with that, call their office and they will explain what they used to do twice per year, and what they are doing now. I feel that we are getting the exact same service with one visit. If you also buy their Care package, your service calls are included on weekends and holidays if there is an emergency (like an insurance policy, if you find that level of service important).

Servicing of AC units ,
 

You are spot on, save your money , this coming from someone that has over 40 year's in the HVAC business.

When it does break down, and it will, see how long it will takes someone to your house to fix it.

Sure hope you've changed your filter regularly though. Can't imagine how crazy dirty it would be otherwise! I personally think twice a year is much better for filter changing, but certainly easy to do yourself.

Same here.

During maintenance visits
 

Yes, that is one of the reasons for the maintenance visits. About one out of 4 that I Service everyday has a weak capacitor The hat I change during the visit. Also if we find the system low on refrigerant we look for the leak and make repairs. Most of what I Service is still under warranty so no charge to customer.
To the topic question, you only need one visits as long as you are changing filter when needed and adding the vinegar to drain line. My charge is 99.95 and lakes me 1.5 to 2 hours for the full service of cooling and test the heating.

One or two
 

Yes, that is one of the reasons for the maintenance visits. About one out of 5 that I Service everyday has a weak capacitor that I change during the visit. Also if we find the system low on refrigerant we look for the leak and make repairs. Most of what I Service is still under warranty so no charge to customer.
To the topic question, you only need one visits as long as you are changing filter when needed and adding the vinegar to drain line. My charge is 99.95 and lakes me 1.5 to 2 hours for the full service of cooling and test the heating.
For those that do not get their system serviced take a look inside your air handler sometime. Most are filled with mildew. This is very typical in the air handler. This grows all over the wiring, labels and the plastic parts.
Really not trying to be smart but your air that comes thru the vents that you breathe everyday passes over this. Some people don’t do a lot of things like get their teeth cleaned regularly. I choose to keep things as clean as I can.

what company are you with

If you are up for changing your filter a couple times a year and making sure your drain line is open, there’s really one main reason to have a service contract: if something goes wrong, you are already their customer, so maybe you will get a faster response time.

Of course, there are also people who pay thousands for a home security system in one of the safest towns in the U.S.

(But who am I to talk. I have both hurricane coverage and flood insurance.)

Twice a year by Munn’s. Well worth the expense IMO. A/C still running faultlessly after 14 years.

Munn’s inspects annually for less than that - no contract.

Once per year.

It is "Preventative" maintenance.

I check my filter once a month and probably replace it every 2 to 3 months. Once a year is not good. If you have an outside air intake filter you can probably check that every 3 months.

Make sure you tend to the drainage system each month.

When we asked the service person we were told twice a year is a waste of money down here. Just change your filter