Dynon customer service
I think you are worrying for nothing. Dynon will repair units after the warranty. They are likely going to be a player in the EFIS products for some time to come. Repairs, if needed will be done quickly and at a very fair cost. So far they have proven to be very reliable.
Talk to any customer and you will get the same story, Dynon has very good customer service. Also they have a great product and will be around, but you are right the manufacture is the only place to get it repaired. However ask again and Dynon customers will tell you they are very reliable. Perfect? No. There have been some small problems, but from what I have read they are always handled very well and at little or no cost to the customer.
I have not flown with my Dynon yet, but have asked them questions, including "what if's" and getting repairs. I feel confident they will turn it around quickly and at a very low cost, even out of warranty. I also have a GRT EIS-4000 engine monitor and have been very happy with their service. GRT of course makes a competing EFIS with more features, but at a higher price. As with any small company making an EFIS, the service will come from the manufacture. The key is if they will be in business years from now when you need it. These units are all experimental. You want certified you can pay $16,000-$25,000 for a Chelton and still have no assurance they will be around or have service centers nearby. The two companies I mentioned, Dynon & GRT, have a good chance of being here for the long haul. Make your choice, take your chance.
Cheers George