Bigsteve
To break in your snowblower, run it at full throttle. Snowblow as normal, but if the snow is deep use a lower gear and try not to strain the motor excessivly. Change the oil no later than 2 hours of use, sooner would be better.
As a side not, never run an air cooled small engine at half throttle when under load. Some people have it stuck in their head if they run a lower rpm the engine will last longer. The opposite is true, these engines need to run at full operating rpm for proper splash lubrication and cooling.