John, you may rest assured that this is indeed the case.

4000+hrs in KingAirs, mainly 200s but some time in 90s.

Use of Ice vanes is sound and good advice. On ANY surface.

If you have Raisbeck, then there is no penalty.
If you don´t, you have to stick to the manual, if the A/I on tables allow your departure, fine if not, don´t use the ice vanes on that particular takeoff. To use them as often as possible will save on maintenance.

Hisdudeness

A most constructive and sensible post. To any readers just now reading this thread save yourself from wasting 10 mins of your life you will never get back and skip posts 2 through 21 :ugh:

This might (qualified) be correct, however, IMO, safety overrides savings on maintenance.
One must remember that 90-series KingAir aircraft are certificated under 14CFR23 which absolutely does not guarantee the performance margin that a 14CFR25 aircraft would, in the event of an engine failure on takeoff...IE: you need all the performance margin you can get with these airplanes, in the event of the unfortunate happening.
I have had an engine failure in two BE99 aircraft just after takeoff (200 agl, approximately) and even with autofeather fitted, the climb rate was very marginal, as we were heavy.

I say...safety first, possible maintenance costs savings, second.

I appreciate seeing the reasoning. Thanks to all.
My AFM does not have any guidance on takeoff performance with anti ice on. It has no guidance on the use of the ice vanes on the ground, and has nothing on the use of ice vanes on gravel surfaces.
We generally operate at ISA or below, even in the summer, and are never temperature limited on takeoff, always Torque.
I do see a significant effect on torque and ITT when I open or close these ice vanes after takeoff with climb power set, so the increase in temperature is something to keep in mind since engines generally last longer if they are operated at lower temps.
Here is another question: would the engine temps be higher if they were started with the ice vanes open (handle pulled out)?

No effect on start.