This has been the rule for a while... Or so I thought until reading this thread - I guess I was burned on a few training runs. I agree with all but do not turn it on until 5 minutes pre-start. If one has travelled or has not had the Garmin on for a couple days OR has cloud cover or is starting in a treed area or a down town area.... satellite acquisition can take longer than 5 minutes. Having travelled quite a bit, I would suggest acquiring satellites the day of arrival at a new location. Charging over night. Note that sometimes a USB port can wonk out and/or a hotel electrical outlet that may be on a light may unpower when turned off; so bring your transformer with the USB cable for sure charging. On race morning, turn the unit on before leaving the hotel room or home. I offer this as I have been in a corral once waiting for the satellites to come in and thought I was about to have to take off without the unit being operational.