Hi,
I don't know about the longest ever, but the longest total solar eclipse
for this century already happened - it was six minutes and 39 seconds
back in June 2009. I am sure even that felt short for the people
watching it. Total solar eclipses are amazing and they go by so fast!

Looking over some eclipse charts I see there were some over 7
minutes in the last century.

The Moon is very, very slowly moving away from the Earth, which means
that over millions and millions of years the durations of total solar
eclipses are getting shorter. Some day the Moon may appear too small
from Earth to cover the Sun completely and then we will will not have
total solar eclipses from Earth's surface anymore. That would not be for
a long time, though.

Terry