My experience is different. I don't wait for the sleep light to disappear, but rather plug the machine back in straight after it has fallen asleep from exhaustion.
Throughout the whole time, you can use the machine. Charge it up, pull the plug once it has stopped charging, wait for it to fall asleep (wait until after the reserve battery warning and yes, you can use the machine throughout this time), then plug it in and charge it back up to 100%.
All up, the only downtime you get is that second when the machine falls asleep. You can plug it straight back into the wall though, and be on your merry way. 🙂