I normally try and do “fun” work. This largely depends on how autonomous your job is. I was a PhD student doing research for a company and I received very little oversight for 3 years.
The supervision I did receive was great though. They understood needing to take a break and slow down. At those point I would generally read papers, watch PyData talks (highly recommend them, like inspirational ted talks for data people), or contribute to open source to learn about new tools or design paradigms.
I think this is the beauty of federation. Everything is open and free to all rather than a company being able to lock in your personally created content.
For example, I wanted to learn about NLP and am working on building a bot to monitor sentiment and check for hate speech in lemmy content. I am still at the brainstorming/research phase, but the accessibility of lemmy makes it really nice.
Pythorhead was made for this exact purpose.