Keep an eye on baby's movements and how you feel.
With both my DCs I had BH from 24 weeks. Every night. Every 3 minutes, like clockwork. With DC2, I thought my waters had gone at 24 weeks so went to hospital where they felt my BH and were very concerned i was in early labour, steroid injection etc.
I wasn't, it's just how my pregnancies go. They would occasionally be very strong as well to the point where, in the later stages I would lie awake at night wondering whether this was it.
Both my DCs went overdue 
Also, the BH would go on for HOURS sometimes 3 days at a time. It's just what happens when I'm pregnant.
Drs just told me to chill out.
What I'm trying to say is there may well be no cause for concern even if they are frequent and last ages. HOWEVER it is always worth getting checked out if you've not had them lke this before.
No , you don't have to call them and they can't stop labour once it's started anyway, but it is usually better safe than sorry. If you decide not to call them just try and sleep, warm milk or something, relax, try not to think about them. They can be a bit like hiccups and go away if you ignore them