It depends on your charter or mission as well as your long term vs. Short term objectives. If your mission involves a larger more expansive view - then you will need to spend a lot more time on unique problem solving that has a strong potential ROI feeding the fulfillment of the mission.
It kind of boils down to ROI (return on investment) vs. risk for me: I look at the ROI and risk (opportunity cost) for almost everything that I choose to do - this helps me compare various choices for what to focus on daily, weekly, monthly and yearly.
Having clear objectives for the month, week and year also help in selecting what percentage of time as per your question. If the solution of this problem feeds the fulfillment of your objectives vs. the solution of this problem prevents a risky situation: that may be the question to answer.
I hope this helps. Feel free to interact so that I can delve into the complexities and nuances that are inevitably there.