erc-lurker-cleanup-interval

erc-lurker-cleanup-interval is a variable defined in `erc.el'.
Its value is

100

Documentation:
Frequency of cleaning up stale erc-lurker state.

`erc-lurker-update-status' calls `erc-lurker-cleanup' once for
every `erc-lurker-cleanup-interval' updates to
`erc-lurker-state'. This is designed to limit the memory
consumption of lurker state during long Emacs sessions and/or ERC
sessions with large numbers of incoming PRIVMSGs.