I quit cig. smoking almost 2 years ago w/ no medications, lapses, or urges. what is relapse rate per yr after 2 years? is it about 10%/yr the next year then decreasing to <1%/yr after a decade. true?

Varies greatly: Depending on age, sex and length of smoking history, but in general, if you stay away for 6 months, the risks of relapse are about 10% over a couple of years, and then go down markedly. Very heavy smokers with long smoking histories are at greater risk of later relapse, as are those with underlying depression.

Congratulations: You are doing well. This is the best decision you have made for your health and wellness. I do not expect you to be at risk for any relapse as you will realize that you never want to get back in to this dirty and unhealthy habit. People who quite on their own and without any help/medication have near zero chnace to have a relapse. So you should not think/worry about that any more.