Spending 4 Hours a day on Musing does not sound unreasonable. It is difficult to be mindful of time when you read the answers to important questions you personally have.
Furthermore, you may find that while formulating an answer to a question, time can go by quickly as you are deep in thought. A well-crafted and thought out answer takes time to write.
On the other hand, 4 hours may be excessive if you have other obligations that require your presence, or if you are not interacting with others. In the first case, you would be shirking your obligations. In the second case, your time would go unrewarded..