Depends on what's going on.
My office policy is that we try to return all client inquiries before the close of the following business day, and we also copy our clients with all correspondence we receive or send on their cases. We also bill our clients for conversations with their attorneys, so if a client calls up, for the third or forth time, to ask a question which we've answered to 'em, in writing, twice before, we'll point this out.
There is no hard and fast rule about how often your lawyer should be in contact with you. A simple divorce can take a long time and if your lawyer has submitted all required documents to the court there is really nothing else he can do but wait. I practice in SF where even an uncontested divorce can take 3-4 months for the court to process. When I handle that kind of case I try to write my client once a month so he/she knows things are moving forward, even if they are moving slowly.
Every lawyer and every case is different and there's no rule about it, but your lawyer should be billing you on a monthly basis, and if the bills are properly itemized, those should give you some idea of what's going on in your case.
If you're not getting enough feedback from your lawyer, call or write the office and ask for the status. If you're not already getting them, ask for copies of all pleadings, discovery and correspondence that get filed, served, sent or received in your case. You may also be able to check your case online on the court's website, if divorce cases are available online there.
Disclaimer: Please note that this answer does not constitute legal advice, and should not be relied on, since each state has different laws, each situation is fact specific, and it is impossible to evaluate a legal problem without a comprehensive consultation and review of all the facts and documents at issue. This answer does not create an attorney-client relationship.