mh-speed-update-interval

mh-speed-update-interval is a variable defined in `mh-e.el'.
Its value is

60

Documentation:
Time between speedbar updates in seconds.
Set to 0 to disable automatic update.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 8.0 of the MH-E package that is part of Emacs 22.1.