Interestingly, in recent times we've been putting some effort into stressing to R22 students the fact that autorotation should not be the automatic reaction to any suspected problem.
This is because we've had a number of fatal accidents in the UK involving pilots who entered autorotation because of a red light, or other perceived problem, and who then screwed up the auto one way or another - let the revs go to hell or ran into the side of a house. (This should also be taken into account when you consider why one in five R22 accidents is fatal. You're not dealing with high-time hotshots here).
The story now is - nose flicks left, engine failure, lever down. Nose flicks right, tail rotor failure, lever down. Anything else and you've got time to think about it before you commit.
As to R22 inertia, Tim Tucker waited an electronically-measured 2.4 seconds after throttle chop before beginning to lower the lever during one test, described to me as "in cruise flight." (Don't try this at home). The 1.1 seconds often quoted as the time you have available to rotor stall is if you seek to maintain height by raising the lever. The three main causes of low RPM rotor stalls are overpitching, rolling the throttle the wrong way (mostly in the pre-governor days) and gripping the throttle so hard that the governor was unable to turn it.