Silencers have some strange laws in different states, so make sure you know what your local laws are. In some states it is legal to own one, but illegal to use one. 
As for battery life on an illuminated reticle scope, I haven't shopped a lot for them, but have noticed around a 4 hour battery life. I'd say that is a good amount of time when considering how long you would actually use it for. It could come in handy in the darkness a time or two. I know some even use the CR123 batteries that my GLV uses . . . although Mutt has almost gotten me convinced to go with the Darwin, so that removes the shared battery factor.
As for battery life on an illuminated reticle scope, I haven't shopped a lot for them, but have noticed around a 4 hour battery life. I'd say that is a good amount of time when considering how long you would actually use it for. It could come in handy in the darkness a time or two. I know some even use the CR123 batteries that my GLV uses . . . although Mutt has almost gotten me convinced to go with the Darwin, so that removes the shared battery factor.