There is no theoretical limit to the number of stops a Driver can do, provided that your subscription plan allows for it.
Remember that you will set a certain Working availability for each Driver. This means that if a Driver works from 8am to 4 pm, all the stops you want him to do will have to be included in that time span, also considering how long he will have to be at each location (delivering a package definitely requires a shorter Service Time than installing an Air conditioning system - Do you want to know how Drivers are defined? Read here).
Also, make sure that the vehicle's Load Capacity (if relevant) is respected.