What to do as a Theoretical computer science PhD student in a free time? I am a mid-stage theoretical computer science student. Although I have a busy schedule, I still have a one or one a half hour in a day which I devote to reading and solving the question given Jeff Erickson's lecture note etc. I am doing this thing from many months and wondering. Is this a right thing for me to do in free time as now I am a Ph.D. student not an undergraduate student. Now why I do this to become more strong in an algorithm, discrete maths etc part. Another thing which seems more valuable to me is to read more and more research paper of my research domain as my goal after my Ph.D. is to publish more quality research papers in the field related to my current field. I am wondering which one is better or suggest anything else which may be more valuable to me keeping my future perspective in mind.

Question: What to do as a Theoretical computer science PhD student in free time? I am wondering what star experienced researchers do in their time ( assuming they have a free time ).

Some of my free time I also spent on watching video lecture of workshops related to my field.

After looking at all the comments and answers, I have to edit my question. I think, I have not been able to convey what I was trying to ask. My question was how to sharp my technical skills in the free time for a better future. It has nothing to do with my personal life or some one's personal space. I was here for the various possibilities and opinions of users, who have experience in theoretical computer science. Let me clarify my question further, I was to trying to ask in the free time what is more significant to do " continue to think about the research problem at hand or do the problems related to maths or algorithms " and so on. Looking at the comments have made me realise that definitely I need to improve my writing skills also.
I strongly agree with other comments that over-optimizing your time is not healthy and your brain needs downtime, preferably social interaction or physical exercise. However, if you feel you have that covered, what I think separates good from great researchers, is having an overarching vision; a generic direction, or specific goal to strive to. To see the forest for the trees, if you will.

One way to achieve this, is to reflect in those moments of spare time; to philosophize very generically on society and identify problems in it. This can range from wicked problems like climate change and inequality, to more practical problems like cybersecurity (e.g. Heartbleed) and software safety (e.g. the Toyota incidents). Don't worry about staying inside your field if things fascinate you. Read widely to find interests. Read popular media, popular science writing, quality newspapers and see what other people worry about. Read the solutions that are being proposed, evaluate their feasibility, and think hard to come up with better ones. Better ideas can make all the difference. For example, the Rust language is tackling the security and software safety issues commonly found in C infrastructure, the Julia language is focused on solving the two language problem in scientific computing and improving the state of the art in data science and machine learning, while Elon Musk's Tesla is aiming to accelerate the advent of sustainable energy in order to counter climate change. Each of these admirable projects started with good research ideas, by people committed to a higher level ideal. Finding your higher level ideal is what you should focus on.

A higher level goal will motivate you to get up in the morning, shape your career in a given direction and give you a sense of purpose and satisfaction. Most likely it is not something you'll settle on in a single afternoon. It is something that requires plenty of reflection, that can shift as your knowledge of the world shifts, changes as your priorities change. If you're ambitious, a good question to ask is "What will have the greatest positive impact on the largest amount of people?". Go crazy, get creative and consider scifi: "Maybe I should solve the inequality problem by writing a Decentralized Autonomous Organisation on Ethereum that unconditionally distributes a Global Basic Income to all." If, however, you are somewhat more realistically inclined, you might just choose to work on Blockchain tech because you believe in its huge potential for leveraging social benefit.

Maybe you are satisfied with something lower profile, that concerns you more directly, which is perfectly fine. What matters is that you find it valuable and worth spending your time on. These are the same principles successful entrepreneurs use to identify possible projects; two considerations are "Am I passionate about this?" and "What's the benefit to society?" The greater the benefit to society, the greater the market for it will be. A great researcher understands this, and chooses to accumulate expertise towards solving a general, overarching problem in his domain. This will have the largest impact both on his career, as well as society. Whatever you do, don't think a paper at a time, but see papers as building blocks towards an end, and take control of where you're going.