It really depends on the individual job and how much you can do in one day. Ive worked on my own for the past 2 years doing 3 gauges a day (1 and a half to 2 bags each) and managed to get stuff done but it tends to be long days with all of the prep work and i often work saturdays if i need to complete within a week for whatever reason. Good Luck M8!
Works well if the labourer will throw it on with you.
Not so well if he won't. Even then, it goes wrong because eventually he'll decide that you're not paying him enough, so you'll either end up being 2 plasterers or he'll piss off and you'll be back to looking for a labourer who'll chuck it on with you.