how long does false/pre-labour last??

I am a FTM - 38 weeks pregnant today! I have been experiencing BH since about 22 weeks. This past week, the Braxton hicks contractions have started to become regular plus I have had cramping and lower backache associated with them. When they first started about a week ago they were 10 minutes apart. Now they are getting closer together - around 4 minutes apart. I know these are not real labour contractions and I know this is normal ... but should I expect this to go on for another 2+ weeks? Or I likely to start labour sooner because of the frequency of these symptoms? What is the experience of other moms who have delivered? How long did you experience false labour symptoms? Thanks so much for taking the time to answer!!