Nothing wrong with 15+ primes with a cold engine sat outside all night.
Our Astro can take 30 primes before the fuel starts to leave the carby (that is when it is too much).
Our Raven 1 only needs 8 primes when cold and been outside all night, but they all start within 2 seconds of turning the key and no need for external power.
I have also heard of the lift the collective up and prime with the lever still up technique, don't know what difference lifting the collective is going to make!