What are the officer promotion rules in the NG/USAR? Is it required to ETS after 2 time non-select?

No, you can still get selected in later years if you stay in controlled group. The needs of the Army will dictate when you ETS. Continue your Mil Ed, Civ Ed, Assignments, and performance to stay competitive for selection.

I served as a Guardsman for 18 years and I can tell you that the longest you can serve as a captain is 10 years. You can decline you promotion to Major if you are selected at 7 years for 3 years. The reason you would decline is to insure that you make it to 20 years for retirement. But, after holding Captain for 10 years its either get promoted, retire, or get out. If you are non-select and over 18 years you are allowed to continue service until you reach 20 years to retire.

the Guard will find a place for you... the operate a lot different than the active duty folks... and depending on how political you are "there are places to go"...