My eldest started full time at 9 months and my youngest will be doing the same when he's 9 months in January. How fast they settle depends on how many days they're in - full time I'd say my son was settled within a couple of weeks. Be prepared for them to be ill a lot for the first 6 months though, the nursery illnesses are no joke!
He will have settling in days proper to starting anyway. Mine is a minimum of 3 - 1 hr / 2 hr / 3 hr - and you must leave them the 3 hr session x
My little girl will be starting nursery in January, I'm back at work full time from the start of February so I thought getting her in earlier would be good so she can get used to it and I'm off work just incase.