System refresh and lastknowngood

1) I am told that we should restart our NT servers on a monthly basis to refresh resources. Is this really necessary? I hesitate to restart production servers that for whatever reason may not come back up after. What are the benefits as opposed to the risk?

2) I am also told that once the LastKnownGood has been chosen that you should restart your system to create a new LastKnownGood or there will not be one available should you need to choose it again in the event of a system failure.

I would appreciate any HARD FACTS on either of these 2 questions. Thank you!