This may be a conspiracy theory with nothing behind it, but I swear companies send out updates that start to affect your older phone. I've got a Google pixel 2, had it for coming up on 2 years. Once that 2 year anniversary comes up, like clockwork, the phone starts acting up. Battery life goes to hell, some apps cause the phone to crash. It's happened with every Android smart phone I've owned... Nothing will ever be as bad as the early Samsung Galaxy phones with battery life. I had to charge that sucker 3x a day at the bitter end.