Once you have racked up a number of positive feedback comments, it's not necessary to worry about more. New customers just want to get a feel that you are a solid seller with satisfied customers. I get about 30-35% of my customers who leave feedback.
I never go out of my way to solicit feedback. I have, however, included the following in my automated message to buyers:
"If you are pleased with your order, please share your experience with others by leaving feedback. (You can leave feedback by logging into Etsy, clicking on the "your account" menu at the top right of the page, and clicking on "feedback.")"
As a customer, I do NOT want to be contacted, begged, or reminded about providing feedback. Sometimes I leave it, sometimes I don't. It just depends on how I feel, how busy I am, if I feel it's worth the trouble, etc. It doesn't mean I don't like something if I don't leave feedback.