Silly question: how frequently does the moon get hit with meteors these days?
Heh. Continuously. I believe your question pertains more to strikes large enough to cave in one of these lava tubes, in that case, not as often, but there’s not much of a system in place to monitor such impacts.
http://www.freerepublic.com/focus/news/809572/posts
http://www.freerepublic.com/focus/news/848926/posts
http://www.freerepublic.com/focus/chat/1216757/posts
http://www.freerepublic.com/focus/news/1313256/posts
http://www.freerepublic.com/focus/news/1546568/posts
About the same as earth gets hit ... :-) ...