I have some doubt whether this topic of Ball Lightning is allowed to appear here in Classical Physics according to PF guidelines. It may be Skeptism and Debunking is the correct place.
As for the question in the OP: BL has been observed to last for many minutes. I have personally interviewed nine persons who have seen BL in one region of the Brasilian Amazonia region of Tocantins. One witness described a circular array of “balls” hovering above an orchard near a waterfall that lasted around thirty minutes!
There is no doubt that ball lightning exists, but no satisfactory scientific theory has been found to explain it. There is no experimental evidence to examine because it has never been successfully created in laboratory conditions. We have only anecdotal evidence from the reports of hundreds of eyewitnesses to analyze. For example: http://amasci.com/weird/unusual/bl.html and http://amasci.com/weird/unusual/blold3.html
Martin A. Uman, who has been acknowledged by the American Geophysical Union as one of the world's leading authorities on lightning, has devoted one chapter in his book to the topic of Ball Lightning. IMHO it is the finest scientific description of this natural phenomenon. https://www.amazon.com/dp/048625237X/?tag=pfamazon01-20