> Don't upgrade your phone. Seriously.
The market makes this easy nowadays. Unless your phone is broken/severely outdated there is next to zero benefit to upgrading at this time. Prices for flagships become prohibitive as well.
Upgrading phones every 1-2 years is a dead tradition outside of contract incentives, only relevant to hyper enthusiasts (r/android etc...). Even then I am not sure why aside from corporation benefits. The differences are marginal at best (ok, Candy Crush 4D gets 8fps more nowadays), the value of upgrading has declined for years now.
Of course these statement will have enthusiasts screaming and foaming because the newest FiveMinus 8T has 1mm less bezel while sporting 25 mAh more battery compared to last years model. Also NIGHT VISION CAMERA! All the not-quite photography-enthusiasts are salivating and throwing their money at phone makers year after year in order to participate in blog-jerk-offing and karma whoring.
People who care about photography get DSLRs, people who care about functional functions in phones haven't had to react to significant changes for several generations now, unless lack of security updates (cough Google) forced people to. WhatsApp, Instagram, Firefox, Mail, Dial, Weather, Auth Apps, ToDo, ... they all run fine on still supported iPhone 5S/SE or older supported Androids. What app that an iPhone 5S cannot run is even truly useful and missed?