I'm 40+2, and have been having mild contractions since last Tues. Last night, they kicked off and were very strong for about an hour and a half. I was almost convinced it was real labour, as they were 5 minutes apart.
Of course, it all calmed down and I haven't felt anything but backache this morning.
It is driving me insane - how long could this go on for? I was 2-3cm last week, with a favourable cervix. 
Any advice/experience very much appreciated.