Moved on to other things too. Like forums. Piano's like an old passionate flame - only hurts when I return to it.
I've never practised consistently. I always binge practised and it failed me eventually, but it did work for quite a while. If I had consistently binge practised (instead of actually *dwindling* over the years till I did perhaps three hours every month or so), perhaps it would've continued to work.
I know all the professors say 'AT LEAST four hours every day', or some other number. But unless you're actually planning on becoming a concert pianist, I don't think it's necessary. To be the best you can be, sure you have to put in the effort. Otherwise, to simply get a goodish pass you can approach it like anything else.
If pieces bore you, do technique. It'll put you into the zone a whole lot easier, I find. Mindless practice is never the best sort, but it's better than nothing, and it keeps your hands in check. I actually find repetitive work like that has a tranquilising effect on me. Also leaves your mind free to do whatever else you want to. If you add in enough variation in tone, dynamics and touch, you won't need to do much more than learn whatever piece you've been assigned till you get to the point where you have it 'figured out', and your technique will be good enough to see you through it at an acceptable standard without too much work on detail (which alternately exhausted and energised me). You may not be your professors' favourite student, but they won't hate you.
Also, Ti is always weighing and troubleshooting. If repetitive work doesn't calm you down or make you happy in any way, then make sure you're fully engaged. There is a LOT to be gained (as I'm sure you know) from detailed work, and it's very stimulating to Ti to constantly refine what you're doing wrong, because it requires analysis. Approaching it mindfully might work better for you.
Basically: binge practice can work, repetitive technical work with enough pre-thought variations will get you through, and mindful practice can actually be *very* mentally stimulating to an INTP. I'm not sure if any of that is useful - perhaps/probably you already know it all.
The problem that remains is getting yourself to the point where you're engaged in that process. Involving yourself from a static position is something that will take effort. Ti is not the way to get yourself there. You will argue yourself away from the piano every time, either by wasting the day talking rubbish to yourself in your head, or finding reasons to procrastinate and do it later/not at all. Unfortunately I know the failure first-hand, but not the success. When I was motivated, I was tremendously motivated and didn't need tricks to keep me on track. When I wasn't motivated, I just flobbed around and gloobered myself into the ground.
One thing that *did* work for me: setting specific goals for each day. Like "today I will perfect dynamic progression in this phrase on page 1 of the Bach (Ti in process); learn two pages of the Beethoven (sheer fucking work, but Ti is involved too); analyse and mark out the major sections in the Rach's musical development and create a logical vision of the piece based on that structure (very Ti heavy, you should love this); and perfect the quality of my staccato in the Bartok (again, Ti in process)". Once I set the goal, it became much easier to work towards and accomplish, and your functions should step in naturally to help. *Especially* with the apparently boring detail work. Developing a method to create a particular aural effect requires a lot of analysis and innovation (down to movement tempo, tension, involvement of the body, etc). What sucked for me was being told exactly what to do. If that is what's happening with you, I sympathise, because then the technical/detail work really *does* become reminiscent of a trained monkey's drudgery. However, if it's *yours*, you will be much more excited about it and inclined to keep working. Putting what you've taught into practice always requires some thought though, so it's not a complete dead-end.
I was weak and let the overly precise instructions from teachers get me down. Don't do that; find some way to make your playing your own (not just musically but technically too, as far as that is possible), because that will activate your Ti and give you the continued interest you need. At least if mindless practice isn't fun for you (as it often is for me).
So: goals and involvement. But maybe you don't really want to be in the world of classical performance (I assume that's where you are). After a while, all my problems aside, I found it stifling and sort of dead. I found other avenues of music so much more rewarding, alive and creative. What you love in music might not be at all reflected in the work you're doing.
Still though, a degree's a degree. Apparently music degrees are looked upon pretty highly by law schools. (I think they were second or third on the preferred list in America, because of the high level of discipline involved.) That might be of interest to you (although I'm guessing that's even MORE drudgery to wade through that you would hate). And if not, it could be better to just get through this regardless, maybe switch your major away from performance to something more theory-related since you easily excel there - the piano aspect would require less real work and it's less suffocating. I mean, Ti-heavy analysis and refinement aside, after a while you just get to thinking if you really want to spend hours every day, by yourself, in a small sound-proofed room perfecting one phrase over and over and over. Is that what you want to do with your life? It doesn't stop even at the top, though it does get easier. Hammering on a piece too much always ruins it for me anyway; even many years later it retains a withered, wilted feeling. I remember this (mangled) quote from a member of an orchestra: "I've played so much I can no longer feel the music. All I do is scrape out notes." That's not where you want your love of music to take you.
Alright I've blah'd on far too long. Why are you in this course, btw?