Difficult one to answer as there are so many variables, weather, how much solution put down, type of carpet, level of soiling, can you leave windows open to help drying, central heating.......... to name but some.
I started off with an Airlex Pro 130psi, moved up to a Scorpion and got a Storm in March this year. One thing I would say is that drying times are a quite a bit dryer with the Storm as it removes so much more water, as a rough rule of thumb synthetic carpets are dry in around 1 - 2 hours and wool in around 2 - 4 hours compared to when i first started.