The most effective routine is the one you stick with for sure!

I love anki and use it for Spanish which is showing marked improvement. I do vocab and conjugation with Anki.

Then I just find other ways to immerse myself and call it a day.

- Spanish audio for sports whenever possible - Interfaces for personal computers/devices - Picking up the Spanish language weekly from the little box on the corner - Listening to Spanish artists - Reading the news in Spanish instead of English (One major benefit here is consuming far less news) - Writing notes for work and personal projects - Texting friends

It all really adds up over time and is definitely doable even as an adult, but it requires a ton of work, so being able to find ways to incorporate it into the activities I'm already doing is key for me on top of the more active Anki learning.