Sorry, I really don't think there's any way to know
for sure. My second labor was just over two hours, but my
third (six years later) was five hours (and my first was
45 hours).

I'd settle for 5 over 2 any day, just a little bit more time to make sure
everything is ready to go, like the midwife is actually there, rather than
still on her way!

to the original poster, there isn't much way to tell, and you don't say how
early and how small your baby was, which could make a difference, plus with
early labours first time mums often don't notice the early signs which you
probably would this time, it would be very unlikely for you to suddenly have
a very long labour, unless the baby was malpostioned, or something else. I
would have thought that whilst active labour could be less than two hours
you are likely to have some warning (my mum for example had a show 8 hrs or
so before my sister was born, though active labour was around an hour).

cheers

Anne