Once a month actually, and only if the patches were applicable. It really is not as bad in the MS world as you think. They made great strides in both stability

Once a month actually, and only if the patches were applicable. It really is not as bad in the MS world as you think. They made great strides in both stability and security over the past 8-9 years in the server OS area. And, I say this as someone who has literally nothing to do with them on a daily basis anymore.