Going way back into the 1-16 sets, a lot of people probably experienced a "jump the shark" moment at the 14th/15th transition too. 11th was weird with the magazines, but I remember that one being out for such a short time, and 12th dropping right away, which looked and felt SO much like series 8 in its gags, and brightly-colored art (even the bright checklists again!) that I remember it pulling me right back in as if the weird magazines never happened. A complete 11th just sat in my box, not getting much replay, but it was a bump in the road. Then came 13 and 14, which were reminiscent of much earlier series, too. Put 7 and 13 together, and they look like one set. 6 and 9. 8 and 12. 10 and 14. There's something weirdly common about these pairs, the gags, art, colors, style... and then after a longer delay than usual... BOOM! Series 15 hits. Back to the whiteback stickers we hadn't seen since series 2 (for those of us who only saw 3rd, 13th and 14th tans), and the art was somehow different. Still Wacky. Still good. But different. The cans and packages seemed more airbrushed, and the puzzle was weird. And it didn't seem to last very long either. You had to just buy all the packs you could or you didn't finish it. Then silence... Wackys were dead. Star Wars came out. Darth Vader was way cooler than our old stickers now. Then suddenly, out of nowhere, 2 years later, Harrison Ford reprised his role... I mean Wacky series 16 came out. And it looked and felt like something not-Wacky.
...and then of course decades later, Harrison Ford AND Wackys reprised many times again...