I have not come across any guidelines, however I insist on annual physical qualification using an appropriate PCD load (to demonstrate stability of the sterilization process), accompanied by a document equivalency review to demonstrate that the bioburden has no shifted significantly in terms of absolute numbers and the presence of spore forming contaminants; and then a bi-annual microbiological requalification, also using a PCD for each product family. I don't believe an annual micriobiological revalidation is a realistic tearget as it is so onerous and labour intenive.
I believe that the frequency you choose must be based on stability of the bioburden on your product - if you cannot demonstrate that, then you have no way of justifying a longer revalidation interval. However IMHO, three years does not sound unrealistic, as long as you can justify it this way.
Jimmy