I asked this same question when preg with my DD (agree speculating is fun! )

First preg (DS) 24/7 nausea for 12 weeks, occassional vomit. All good from 16 weeks, no nausea at all.

Second preg (DD) 24/7 nausea and vomiting for 24 weeks, hospitalised to be rehydrated, on maxalon and cyclizine until 24 weeks, continued frequent nausea and occassional vomiting until 36 weeks