Check the program and see if the ramp rate is set to 9999 as suggested. Beyond that, it takes time to heat up the well insulated refractory lining. This is also why it takes a long time to cool down. The listed max being 1150°C is sometimes like the speedometer on my car going up to 120MPH.
Generally, I prefer a slower ramp rate and more even temperature control on my stainless HT regimens .... especially as it approaches the target for austenitization. Remember, the TC reads the air temp in the oven , the blade packet is larger than the TC, and is absorbing the radiant energy from the coils faster. Thus, the two are not necessarily the same temp if the heat is being applied at the max rate. On the ramp from equalization at 750°C to 1050°C, the blade may pass the target by a good bit before the TC equalizes the chamber atmosphere with the denser blade steel. The slower ramp rate helps prevent overshooting the target. If a fast ramp is desired, make it fast from 750°C to 900°C and then slower from there to the target temp.
The lower ramp rate does not really affect the regimen time much. Say you are going from 750°C to 1050°C. At a ramp rate of 9999 the oven will take 1.8 minutes in theory. We all know that isn't going to happen. Setting the rate at 3000 will still get there in about ten minutes. The overshooting will be less, because the slower rate is more realistic than trying to heat it up beyond the capacity of the refractory to absorb the heat.
I did manage to heat treat 9 blades this evening, including a 12 inch kitchen knife. My old oven would barely fit 7 3/4" 
