DNA will bust your balls if something goes wrong under warranty and you have worked on the bike yourself or had a non-cert tech do it. You will be screwed even if you or the non-cert tech are competent mechanics. It's a major "out" for DNA to fix anything under warranty.
Magnuson Moss Warranty Act of 1975 disagrees with you. They have to prove that your work on the bike caused the problem that you are trying to have covered under warranty. Do I recommend that everyone check their own valves? make the beast with two backs no! But a manufacturer cannot void your warranty because you let Randy change your oil