Why do you focus on how long it took to make? For pieces that large, I usually take upwards of 10 hours, but it really doesn't matter how long it took. If anything, being proud that you rushed it is a negative, not a positive.
Anyway, for the piece itself:
Linework is decent, except in a few areas, such as the jawline being a bit weak and irregular. The palette is probably fine, though I'm not sure I like the yellowish tint to the skin, it's just a bit sickly. The shading is not very volumetric, you could work on that a bit more probably, though there's already a solid start there.
The main issue is banding. There's banding going on everywhere and it really detracts from the quality of the piece, making it even look blurry in areas like the eyes. Read up on banding here:
http://www.pixel.schlet.net/