I feel that 2 1/2 months is far too young to be self-settling. IMO a baby that young needs comfort from his Mum.
I think it depends on the child. DS is 4 months now and has been self settling for weeks now. If there is any sign of distress from him, I go straight back in - he tells me if he needs me, but most of the time I wrap him, give him his dummy and walk out. He goes to sleep without a fuss.

Ezz - both my babies have done the one sleep cycle thing!! It drives you nuts but with consistent resettling, they do learn to put themselves back to sleep without you having to help them. DS is now able to do this often on his own, sometimes I still need to help him resettle but I know from experience with DD that they do get it eventually with lots of help from mummy along the way!