Learning from Online Blitz
I'm not a blitz addict. Really. I only have about 500 games played over the past 4-5 years since I joined chess.com.
One of the reasons I don't play a lot of blitz is that I have many other chess activities that I think provide better learning opportunities. I'm not sure I've learned much from my infrequent midnight blitz binges in the past.
But, I know I can learn something from blitz, if I approach it the right way. I can learn how to quickly recognize those tactical motifs that I've learned from solving tens of thousands of tactics puzzles. Most of those tactics never get played out in long time controls but in blitz devastating pins, skewers, and knight forks abound.
I can learn how to keep my pieces safe. An unprotected piece in blitz is a future hung piece.
I can learn how to win an easily won endgame quickly--through muscle memory. Think Q+K vs K or B+B+K vs K.
I can learn how (blitz) players will react to my opening choices, giving me many positions and lines to look at after the games. Unfortunately those openings are often not ones that I'll see OTB.
In order to learn from blitz, though, I need to be disciplined in reviewing the games afterward and look at the mistakes and opportunities each side had. I need to look up the opening play in my repertoire or in a master database. Without doing those simple things, blitz is little more than entertainment.
And, by spending time reviewing each game, it discourages those mindless binges that we all get caught up in, trying to win back our rating points, like drunk gamblers in Vegas.
Here is a position from one of my blitz games today where I learned something as white.