I probably spend anywhere between 10-15 minutes on scales (I'll usually pick one key, and do lots of stuff on that; this is probably easier once you are comfortable with all keys) For example, I'll pick C minor, do some scales, some poly-rhythmic scales (triplets in right hand, eighths in left, etc), some slow, full solid chords, broken chords, arpeggios and inversions. I always like to finish off with a minute or two improv in that key; you let loose and it feels good applying your creativity to the techniques you just went through.
That takes about 10-15 minutes, sometimes more, sometimes less.
If you like working on many pieces at once, you might play through each once or twice, then go on to the next; this could take an hour if you have LOTS of stuff.
I'm starting to get more into focusing on one piece for 45-60 minutes, polishing off every section I come across. In 2 hours, I'll have worked quite a bit on specific stuff in 1-3 pieces. It's harder to do this (because you usually want to play lots of great stuff), but I've found even after doing this for a short while, the quality of my playing is improving drastically. Set goals for your practice: "I want to work out such and such technique" or "Pedalling and voicing" or "Memorizing a section". If you have an idea of what you want to accomplish, practice is just that much more rewarding.
If you like composing, then you probably like improvising. Again, for your warmup, you can make your own chord progressions - try applying techniques into those (C minor chords leading into F minor arpeggios, going into Ab major scales, Eb major chords as a basic example).