I feel like it's called and "Annual Sale" because it runs all year. But to answer your question....according to this page the 80% off annual sale ends Dec. 31, 20??.
With that said, if you see something you gotta have, get it when you can. I have seen items sell out and then never come back in stock. I'd also suggest watching the promotions closely. Prices and promotions can fluctuate. New items are added and rotated through on a weekly basis. Eden always has something on sale. The current 3 for $20 , $30 and $40 promos are pretty aggressive. I also like the buy more save more promos when they have them.