Usually about once every year, which I acknowledge is probably excessive. Main reason is because I like Google phones, and I've been buying the newest one almost every year since the release of the Nexus 5, though I skipped the Nexus 6 because it was simply too big for me. Another reason is because up until the Pixel 3, I wasn't truly happy with the phone's performance; previous devices would always take just a little too long to open an app or accomplish some task. Also, batteries degrade over time and I find that my battery life is not as good as I'd like it to be if I keep it for much longer than a year.

That said, I'm probably going to keep my Pixel 3 for another year, unless the Pixel 4 reviews exceptionally well. I'm not happy that the Pixel 4 removes the fingerprint reader, and I'm concerned that the 90hz display will significantly impact battery life. Also, really I've just been very happy with the Pixel 3's overall performance, so I don't see much of a compelling reason to upgrade this year.

Here's my thinking about smartphones in general... My smartphone is an indispensable tool; I use it to look things up, to communicate with people, to watch videos, to order food, to call Ubers, to listen to music, to read the news, and so on. These capabilities are very important to me, and I see an investment in a new phone almost as an investment in myself. Newer phones mean faster processors and new batteries, which directly translates to less wasted time. Perhaps upgrading every year is a bit much, but I definitely wouldn't worry about having to justify upgrading once every two years.