Yes. They can take as long as they want. Dealing with insurance companies can be very frustrating and confusing. It would be very worthwhile to consult with an attorney who can help you ensure that your recovery adequately compensates you for your injuries.
There is no time limit for an answer, but there are actions that an experienced Missouri workers compensation attorney could do, such as setting the matter for a mediation. These are held before an administrative law judge and usually forces the insurance company to make some response to the demand. Otherwise the ALJ can make the defense attorney call his client and get authority. Without an attorney the insurance company can string you along for a while, until you are desperate for money and will settle for cheap. A good attorney can help you maximize your recovery.