I was thinking about this and it seems like the massive culture changes happen in the even numbered decades and the odd numbered ones tend to be the maturation of trends established in the even numbered decades.  For instance, I would consider the 1920s, 40s, 60s, 80s, and 00s the defining decades for culture and the 30s, 50s, 70s, 90s, and 10s are basically the fulfillment of what was started in the even numbered decades.  The 1950s for instance is known for its rigid traditionalism and conservatism, but that mindset began in the 1940s as a reaction to WWII and the decadence of the Jazz Age.  The '10s more or less have been an extension of the '00s.  Yes, the music is different, the tech is different, and the trends are different, but the overall mindset and zeitgeist has been somewhat similar since at least 9/11.  I imagine that the '20s will bring the next major cultural shift.

What are your thoughts?

I really don't agree with this at all. Every decade has its own distinct identity, sometimes even with multiple major eras compacted into one, like with the grunge 90s versus the late 90s. Speaking of the 90s, I certainly don't see them as just an extension to the 80s, certainly not culturally, at least. They did sort of continue the technological and economic boom of the previous decade, but as a whole completely contrasted to the overall style of the 80s.

The 1950s were also more of a split decade. Beatniks and rock & roll had little to nothing to do with the 40s, except maybe integrating a few scattered influences from that period (i.e., Hank Williams' 1947 song "Move It On Over" being very similar to "Rock Around the Clock"), and actually reflected a highly liberal youth culture that contrasted against the ultra-conservative adult culture at the time.

What about the 1910's? They were VERY impactful to history because of WWI, the event that pretty much kicked off the classic 20th century.