I review my handbook and contract annually - however I only make them resign their contract if I change anything 'financial' in it because I want my contracts for each business year to match my income statements - this is also why I choose to have my rates go from January 1 - December 31 same as a tax year cause it is just easier for record keeping - I do not need to keep two copies of contracts in a tax year reflective of each 'rate' - just need the one.

My handbook is separate from my contracts so I can change that without needing to change the financial contract - I just send them an updated PDF of it for their records.