bb send status LIFETIME Value

[Francesco Duranti]

We have some status messages (for example threshold from mrtg router
monitoring) that are sent only when the threshold are passed so it's
possible that some of them are sent out only 1 times in a month or even
less.
It should be usefull to have the possibility to put a LIFETIME
"unlimited" on a certain status message so that it will never become
purple because the LIFETIME has passed. 
It's possible to set a really big number of week for lifetime but it can
be a good idea to have a proper setting for doing this.

Thanks
Francesco Duranti