My philosophy on being "caught up" has changed a few times over the years. I discovered digital scrapbooking when my oldest was 5 months old, so early on I wasn't too far behind. Back then I used to set a date when a given yearly album needed to be done. (The date was a year or 2 after the time period in the album, so not much pressure!) The last few weeks before that date I prioritized the unscrapped photos and stories I most wanted in the album, scrapped those, and then let the rest go. That mostly worked for me until my 3rd child was born. I don't know if it was having less time or more photos, but I started falling further and further behind.
Then we have the period from 2008 to 2015. During those years I was printing single pages in albums, so none of those years are done. There was no pressure, since I knew I could get to it whenever and add it then. There's enough printed from each year for my kids to enjoy, so I'm satisfied for now. Like Adi said, I'm figuring that those will get done later on, when I have fewer current pages to scrap and more free time due to older/adult kids.
My current pages are the ones I'm stressing over now. In 2016 I switched to photobooks, but I don't want to wait years to finish everything before I can print. I finished 2016 in fall 2017, and now I'm up to scrapping summer 2017. But over the last year my scrapping time has gone way down as we've taken on some much needed house projects.

It's going back up now, but in the fall I'll probably be increasing my work hours. I have yet to figure out how it's all going to work. I love photobooks and want to keep printing that way (plus it motivates me to get more done), but I know that single pages are a lot more practical for me.
Hmmm...how did I start trying to answer an easy question and then end up off on this long winded tangent? Back to the easy answer--2008 with just a few 2007's mixed in.