Apple Watch re-calculate Functional Threshold Power (FTP)

I have done some indoor biking and paired the watt-meter in the bike with my watch. As promised after about 5 sessions the watch had calculated my FTP. Now about a month later, I sort of feel that the FTP value should be re-calculated, but nothing really seems to happen. When I view the settings in the watch app on my iPhone, it just keeps saying the same value and that it was calculated 24. september 2024.

How often should I expect it to recalculate? Do I HAVE to enter my own values, if I want it to change from the current value or will it automatically recalculate once a month or with some other set interval? Will it only recalculate if it sees 5 consecutive sessions that are way above or below the current calculated value? Is there some way to provoke it to recalculate?