Didn't get my streak lingots!
I did not get my lingots for a 130 streak nor a 140 day streak and a 150 day streak . Any reason?!?
Before I stopped getting my streak lingots around day 180, I had never (since my first few days on DL, on a travel day) missed a day. Since then, I have missed three days (and spent 10 lingots for the streak freeze to preserve my streak). This is anecdotal evidence that the streak lingots are a "gamification" motivator to keep me coming back to the site consistently.
Six months, no missed days. Six weeks, three missed days.