I know these are always 'how long is a piece of string' type questions but it's just general curiosity.
With DD1 I started having very low, but manageable, aches on the Saturday night and went in on the Sunday morning to be told I was 4cm. They kept me in but because my waters had gone on the Friday night they put me straight on the drip to hurry the process along. 4 hours after being put on the drip she was with us.
Basically I'm just wondering whether there's any way to gauge how fast/slow it would have been as a regular birth? The midwife seemed shocked that she arrived so quickly and had been preparing me for a good 6 hours more so I'm not sure if that meant it was a 'quick' labour or whether having had the drip renders it all a bit moot?
I'm mainly curious because if DP is away when I go into labour this time I don't want him to rush back needlessly if I'll have hours, but similarly don't want him to take his time if it's going to be a quickie. 
Any way of knowing?