The fastest I ever knitted a sweater was 2,5 days. It was in Cape Town, South Africa and I was freezing my butt off.
When I realized knitting was my thing, I invested in a set of interchangeable knitting needles from Clover. They come in a kit with everything you may need to make most projects. Cables in different lengths and bamboo needles gauges 2.5 mm to 10 mm. It also has stoppers that are oh-so practical when it comes to placing stitches on hold.
Normally, when you knit, you use two needles that are the same. What I do, is making my left hand needle 2mm SMALLER than my right hand needle. The right hand needle is the one that commands the gauge and tension, the left is just a place holder from where to transfer the stitches. What happens when you chose a smaller needle on the left hand side, is that the stitches glide up so much easier, and with less resistance, the knitting goes faster. Try it! I swear, it really makes a difference.