UPDATE: I sent in my watch for a replacement with a new battery after talking to support and so far the standby life has been EVEN BETTER than before, even on 7.2 firmware.
I've been using my Vivoactive 4 consistently since May 2021. I use no HR or other sensors. Simply run GPS for my runs and bikes and have it as a minimal smart watch most of the time. It has consistently easily lasted 6-9 days (depending on how much my sleeves wake up the screen light).
Over the last month i've noticed a sudden drop in battery life. Like losing 25% on my bedstand overnight. Barely makes it passed 2.5 days on my wrist with no GPS activities. etc...
I've turned off all sensors. Use a very lightweight watch face. I really feel it must have to do with the firmware upgrade to either 7.1 or 7.2 based on the forum posts here.