I haven't had such downtime for the last couple of years (working on early-stage startups) but I'd really like them back in the corporate for personal growth as a developer in three ways:
1. Create a new side project unrelated to work, such as a tool or library I always wanted to create.
2. Learning a new stack/domain by creating a product with it. This way, I got proficient in Go language back then.
3. Look around in the corporate and see what I can hack myself for personal growth, AKA intrapreneurship. For example, I went to a CTO office of a sibling organization and asked them if they wanted to do a PoC together with our organization on something new.
If I had such time now, I would look around for a problem in my product/life that I can solve with LLM and try to create a PoC of an LLM product (maybe with a creative UI) that will teach me a lot and maybe get some users.
On the other hand, if you want as a goal to get a position in a FAANG-style company, this is a great time to do a leetcode learning path and get ready for interviews for such jobs.
