Nessus on firewalled LAN

[Adam Bender]

I want to scan a bunch of hosts on a LAN (low latency).  However, a lot of 
targets have firewalls on, which makes the scans take forever.  I've tried 
setting checks_read_timeout = 1 and plugins_timeout = 6, which seems to 
work, but is there any danger in doing this?  Is there a better way to
deal with targets with firewalls?  Turning them off, sadly, is not an
option.

Thanks,

Adam