Best practices for a Board of Advisors depends on the stage your company is at. In general, you will want to bring your Advisors together at least twice a year and call them frequently for specific questions. Some of the specific things to consider include:
Probably the most intensive for an advisory board since plans are in flux. Your interactions will probably be more frequent and in some cases daily until the strategy is flushed out.
Product Launch Stage
At this point, the advisory board may need to change since the skills to launch are far different than the skills to start. Another thing to keep in mind is that the frequency of meetings will depend a lot of the skill sets involved. You will talk more with the market expert than with your technology expert.
Probably the 2nd most intensive point for an advisory board since a lot of the growth strategy needs to be hashed out. Again, the skill sets of your advisory board may need to be adjusted since growth has it's own challenges.
A mature company has vastly different needs than a startup and your board of advisors may need to change again. Maturity allows a company to now branch out into different markets and having advisors that understand those new markets will be a tremendous asset.
The thing to keep in mind is that an advisory board should change when your company moves into different stages. This is important for a couple of reasons: 1) Different stages require different skill sets and 2) Fresh ideas will keep you on your toes.