Well, it's been over two-fifths of a year of practicing Japanese every day.
I'm learning Japanese. I have no idea why — probably because the world's so topsy-turvy right now that I've made it a point to make so many routines as possible. Maybe because I've watched フリクリ (FLCL) so many times that it's become baked into who I am, the very foundation for who I view myself as.
I also really, really love Dance Dance Revolution.
The other thing that makes this whole "I'm nearly thirty and deciding to learn another language" thing more complicated is that I am already bilingual. Well, sort of. I received a minor in French as part of my university studies. I know a lot of French, so I'm able to understand it in the written and spoken form. I was just incredibly lazy while learning it, so my ability to use it has suffered. Nevertheless, while learning French, I also took the time to (mostly) learn the writing systems of Japanese, katakana and hiragana. I've since strengthened that skill so that it's more automatic and natural. My plan is, this time around, to be more precise and intentional in my approach, though I no longer have the formal structure of the classroom to guide me.
A lot of people have good reasons to learn languages. I do not. I think my brain is just wired to want to learn languages,  so I've built a lot of routines around giving myself space to be able to do so. There have been quite a few times where I've asked myself, "why am I doing this?" I have no good answer. There's no one goal that I really have. I'd like to spend more time in Japan than just passing through Narita International, but it's not like that's on my bucket list. 
So: why am I learning Japanese? I don't have a good answer.
Why choose this as our goal? And they may well ask, why climb the highest mountain? Why, 35 years ago, fly the Atlantic? Why does Rice play Texas?
How I study
I study a number of flashcard decks as part of my morning routine, typically while eating breakfast. Today, for example, I studied 184 flashcards in a little under 25 minutes. Anki reports that 57 of those cards and 15 of those minutes were for my KanjiDamage deck.
Anki is the flashcard system you must use. I use it to memorize just about everything, but for Japanese, I'm currently working through the stock KanjiDamage deck. KanjiDamage is a free online dictionary which is extremely inappropriate in its contents sometimes, but contains a number of helpful mnemonics as well as a novel ordering system in order to build on the knowledge that you're making.
I typically learn two or three new kanji per day, and spend most of my revision time just reinforcing what I already know. This is, admittedly, slow progress, but it I feel like I've struck a balance in the amount of time I spend on this every day.
In the evenings, I'll do a little bit of Duolingo in Japanese as well. I typically do this at the same time as the rest of my evening routine, which is a smattering of chores mixed in with a quick workout. I'll probably spend ten or fifteen minutes on Duolingo each night, give or take, so my progress here has been relatively slow going as well.
And, of course, there's other media that I engage with. I hope, soon, that I'll be able to start doing full-immersion-type activities. It's one thing to watch a film or a show with subtitles, but I really felt like I started understanding French when I started playing video games in it. It's not so easy to do things like change your phone and laptop's language to Japanese, though… because if you don't know a kanji, it's going to take quite a bit of effort to riddle it out!
Is this useful?
You may say the best way to learn Japanese is to read a textbook cover-to-cover. Fooey on that. My routines are great for me because they are routines. I would be shocked if I ever give them up. Even on my worst days, I'm still engaging with the process and meeting the bare minimum that I've set for myself — the minimum being a triumph in itself!
Am I learning bad habits? Oh, absolutely. But I still maintain, when learning anything, shortcuts are often good. They set up a foundation which you can adjust over time, while still being able to build on the foundation better and more quickly. The most important thing for me, right now, is building my framework so that it carries me into the future.
So: I don't want to hear anything about Duolingo being bad!
How far I've come
Though I have numbers to quantify how much I've learned so far, it's actually sort of difficult to qualify those numbers.. I'm now over 100 kanji in in KanjiDamage; Duolingo claims that I've "learned" 838 words, but that is almost certainly a garbage number. Looking at a random list of JLPT N5 kanji online, I can look at each one and say "oh, that represents this concept." I probably have the on'yomi and kun'yomi memorized for 3/5ths of them, and probably really need to work on my readings for a fifth of them.
But, of course, my mechanics are probably horrendous right now. This is because of two things: I've mostly been focusing on vocabulary, and Duolingo's more informal approach to teaching the rules of a language mean that I can't point to concrete rules. …Yet! But hopefully I'm sublimating a lot of concepts that I'll be able to put names to … relatively soon.
To some extent, my goal has always been to pass the JLPT N5. And I think I'm on track, if I wanted to consider taking it at the next possible opportunity, which would be half a year from now! But with work and life, I think it would be more realistic to try to aim for a year from now and to set up a study plan to get there.
So I suppose it's just going to be business as usual for a while. I don't want to disrupt any of my routines, but the next step will be that I need to start reading and learning from an actual Japanese textbook, like Genki.
- This is so much different from people who claim that their brains are not wired to learn languages (as opposed to to want to). I firmly believe that nobody has the innate ability to learn languages besides babies. Language acquisition requires an immense amount of training, passion, discipline, and humility. One must elect to strive for those things. I've heard so many people say they're just "not good at learning languages." No. Nobody is good at learning languages.
- Owning a full, arcade-size Dance Dance Revolution cabinet is.