I am sure that the AFM for the B200 I used to fly (but do not have it to hand) specifically required the ice vanes closed for T/O as a limitation. Check your own AFM.
Putting the windscreen heater on in the pre take off checks is likely to prolong the W/S life. It has been not un-common for exec jets to suffer shattered winscreens from time to time. My own research has indicatefd that with W/S heat on the winscreen is slightly more flexible and less likely to shatter, maybee due to fuselage movements. Manufacturer's advice I have received right back to flying the Comet is to have it on to keep it slightly more maleable for a variety of reasons.
MM