Steve it does take pretty much a hour,

Connect hoses, check for pressure, a few other checks, then set the machine going, if it has any gas in it will take upto about 10mins to extract this and any old oil. Then you have a 20min vacum followed by leakdown test of 10mins. Then it will add the refrigerant and new oil, then a check that the system is working correctly, disconnect machine etc.

Before you know it a hours is about done.