When should I convert to Google Analytics 4 or upgrade?
On July 1, 2023, Google intends to stop processing new hits as indicated by GA3, and on October 1, 2023, more unique Analytics 360 properties. After the upgrade, you will only have access to your historical data for six months, but you may export it to prevent a total loss. Starting immediately, you should begin producing useable data since when information is compared to past data, it becomes much more meaningful.
As soon as you can, you should switch, so that you can gather data for comparisons and have information to examine. The time is now to act, so set up your tracking and export your GA3 data while it is still accessible.