It takes a good chunk of time to load 2500 data points into the 6430 to do a sweep. If you will be reusing the sweep, you don't need to reload it. All you need to do is to issue the following command before you run :INIT again:
:TRACe:POINtswhere
:TRACe:FEED:CONTrol NEXT
:TRIGger:COUNt