Doing the actual refactor was probably 25% of the time investment here. When I saw the GitHub launch post about the new UI I started having a few ideas about how it could be improved, so I started hacking on it in Photoshop. Usually these kinds of things just end up in a trash folder somewhere, but I was digging where it was going so I kept at it.
As for writing the article, we actually like to encourage each other to write interesting articles on our personal blogs. One thing to keep in mind is that you'll be most productive when you're inspired to write, so if I get inspired to write something mid-day, unless there's a super important Segment.io deadline I'll just take a detour for an hour and write down my thoughts. And we try to remain open to each other doing that, instead of seeing it as "wasted" time. @calvinfo did the same with his recent article on Node's new streams too: http://calv.info/an-introduction-to-nodes-new-streams/ — since they are timely topics we like to get them out as soon as possible.
Mostly I just enjoy it, so I do it ;) I usually write these after 8pm or so when I switch from working on Segment.io to doing whatever else I want (half the time it's still working on Segment.io haha).
I also wish more designers would write about this kind of stuff, so I like to do it myself too. I'd love to get more process information about how other startup designers think.
I wouldn't worry too much about keeping it fresh... I had a long period of silence from October to March while I was head down on product. Although I did feel guilty about it the whole time...
I think the "after 8pm" part is the secret sauce of not feeling guilty about how you're allocating your time. You've found a chunk of time that you really shouldn't be working on your startup anymore...and it's a time slot where most people are wasting time watching TV, drinking, etc. Keeping productive at that time is awesome.
I like this so much, I might give 8pm blogging a try.
Just make sure to jot down every thought and elaboration of those thoughts as they come to you, no matter what time of day they come. Save post-8pm for going back and hashing them out into a full-on blog post.
Extremely important. The pieces will all come to you in little bits over time, until you have enough thoughts that you can form a longer story.
To manage it, I keep a _drafts folder in my Jekyll  repo which I quickly switch to and from using the project switcher in Sublime. And I use Squarespace Note  to jot down ideas from my phone if I have one while I'm going to sleep.
I believe it's an excellent investment of your time and glad you're doing it. Derek Sivers also wrote about publishing a few weeks ago: http://sivers.org/local it's very high impact stuff, we often forget that.