My skills never decay
I've been on Duolingo for 17 days now and my skills have all stayed at perfect strength. It seems there is no decay for me at all.
When I go to the vocabulary page to look at the individual words, I can see some words do decay. For instance, the word "Flug" loses two bars every day! Actually, it seems to be the only word that actively decays. A few other words decays very slowly, like losing one bar every week.
Most other words do not decay at all. Many words that I only see once two weeks ago still stay at perfect strength.