When I carried twins, I had prodromal labor every night for weeks and I was 5 cm/100% for the 10 days prior to their birth when I actually had my water broke since I was term. And my doctor joked that they really should have just fallen out at some point in that 10 days!
My other deliveries, I also had lots of prodromal labor for at least a week to 10 days of where every night I'd think, "Oh is this it??" and lots of contractions that even got down to 3-5 mins apart but they didn't seem to get any closer than that and it just wasn't quite 'it'. I definitely KNEW when it was time. They felt different and nothing I did changed them. My 'test' was always to hop into the tub, drink a bunch of tea (or cold water when it was summertime LOL) and see if they stayed as regular as when I got in. Because, usually when I got into the tub and got relaxed, they'd slow down and then as soon as I got out they'd go back. But, when it was the 'real thing' they stayed the same in the tub.
I also seemed to get the prodromal labor at night and it would always peter out by 2 or 3 am and I'd fall asleep. When it was 'real', my labors still started at night with the prodromal stuff, but just didn't stop in the middle of the night.
Good luck mama! I think you'll know when it's time, but with twins and being a little early, defintiely go in if you think it might be it. They can always send you back home :)