I recently got in touch with a senior developer at Forem and we got to talking. I asked them if we could pair on a github issue that was posted on Forem's repo and they agreed. It was about a 2 hour call, and all I can say is that I valued that they could spare time to share knowledge.

What I learned

They learn from you as you learn from them.

Small differences in your setup is what will cause this knowledge exchange. If you use VS Code and they use atom, there are things that you can do that they will want to learn how to do as well. If you're still learning a new language or framework, there may be some syntax that you may have recently learned that they forgot. All the while, they advice on your code and how best to express it to be legible to others.

It's fun.

I love learning. I will always take up an opportunity to learn. This means that when I sit down to pair with a senior, it means that I know I'm going to learn something new, no matter how small. And that is always an exciting prospect.

It's eye-opening for both parties.

Sometimes, you may write code and open PRs for review, get feedback, change the code, ... etc etc. That whole process can abstract away your supervisor. You do not get to see how they think through the code. Pairing with them will allow them to ask you questions that make you rethink why you wrote the code the way you did. Conversely, it allows them to understand why you write code the way that you do. This can and will increase cohesion between the two of you. Win win.

Conclusion

Get a day, pair with a senior dev on a project you're working on. Even if they aren't from your team, or your company. It always helps.