As long as you are enjoying answering the questions or asking questions on musing platform it is absolutely okay and there is no question about 4 hrs or 2 hrs. So keep musing on....as long as the questions are pouring in and you know the answer of those.
I personally do not weigh on my activities in hours and I do not even think about that because ever since I came to know about musing I have really improved my activities in steem blockchain and especially in musing and it is not like that i do not read, apart from answering I read a lot of questions and answers here and read the whitepapers of good blockchain projects and that gives me a lot of pleasure and from my 2 years of experience what ever I know, if I see a question related to that I promptly answer that, so it is like a online library for me, so a lot of fun, yet at the end of the day I get paid in the form of upvotes, is not that motivating !!!
Therefore it is not about much or enough, just acquire your knowledge as much as you can and you can do that in musing by reading other's questions and answers and enhance your knowledge base apart from questioning & answering and for that there is no limit of time.....it is just unlimited, so be a flow in the limit-less musing platform.
Thank you and Have a great day.