I'll also finish my revision probably by the end of February, and will start past papers soon, possibly in start of March.
Yes you should start as early as possible, it takes a lot of time to solve one, read mark schemes etc. and it depends upon your aptitude too. Like if you have a strong grip on your concepts, you may even be able to solve 5 papers a day, but if not, then you may spend as much as a whole day on just one paper!