I think they already reached a stage in their lives where they don't need to aggressively promote their material as compared to other artistes
they're the best selling artiste in Japan of all time & you can be certain that whatever material they release next , they will get the #1 spot , 99.99% of the time
anyway Koshi's Okay solo single has been certified Gold for shipment of 100K copies
http://www.riaj.or.jp/data/others/gold/201006.html