I train my ear for about 3 hours maximum every single day. Sometimes it's shorter than 3 hours depending on how much I have accomplished with the exercises. When it comes to aural skills, I believe in just small chunks of accomplishments at a time. How do you eat a big elephant? One small bite at a time.
My aural training routine goes like this:
*I go to this website called iwasdoingalright and I do a bunch of exercises with melody recognition. What I like about this website is that it is a call and response type of ear training. A melody plays and I have to respond by playing the same melody that was played. I work from one single note till two notes and sometimes 3 note melodies or more. Then I work with harmonic notes. That means notes played together. I asses myself by using a 7 minute timer on my cellphone. If time runs out and I made only 5 mistakes or less, then I make the exercise a bit more difficult the following day. I play the answers with a piano, while I do this exercise.
*After I finish the exercises with iwasdoingalright, then I learn a tune a day. That means I transcribe one simple to transcribe song every single day. I have been doing this for 40 days straight. This exercise builds the mind, ear, solfege, and finger coordination. How much more if I have done this for 365 days straight. I have my own system for reviewing previous songs that I have transcribe. The songs I have transcribed I keep the titles on an excel file. Right now I am transcribing songs played in the church, because they're simple and diatonic and easy to transcribe. I am at that phase right now. Later on, I will do more complicated music as my ears improve.
*After I learn one tune, then I spend 10-11 minutes with some solfege exercises. I learned these exercises from Ron Gorow's book Hearing and Writing Music and Adam Nitti's ear training exercise.
*Then I work with chord progressions and changes. I play actual chord progressions of a song and I sing along, and I play the changes from memory. This builds my inner internalization of the chord changes and their subtle nuances. I keep the titles of the songs that I have memorized on an excel file. I have my own system for reviewing previous music.
*Then I do some vocal exercises to improve my singing voice.
*Then I work with Chord Identification. There was a professor in my school named Ron Westray, who gave me a chart of every single chord type in the world. With a 20 minute timer on my cellphone and an excel file, I play every single chord. When the time is done, I put a check mark of the chord that I last left off and continue the next day. When I have completed every single chord I go back to Major Triad and play with a different root note other than C like F, Bb, Eb, Ab, etc. With my jazz piano lessons with Amanda Tosoff, I am able to play chord voicings that are used by the pros.
*Then I use this flash card software game called Anki for internalization and familiarization of the piano. I also play guitar so I work the same thing with the guitar too. I put some single notes, Like C4 B5 E2 etc, then I work with harmonic notes, then I work with all the types of piano chords. The Anki software will ask me random questions based on the question that I have placed. Anki is originally used to help us learn languages, but it works for music too.
This takes me a maximum of 2-3 hours every single day. I recently purchased a CD called Play What You Hear by this British Jazz Guitarist named Chris Standring. When it finally arrives at my home, I might end up practicing aural skills for 4 hours with this new method of mine coming up.