My, and at least a few other, 740 shuts down immediately if the screen is left at 100%. I know that the bright screen is an important feature of the iFly series, but IMO, the ability to remain on during breif power interruptions is also and important feature.
I would like to suggest that, until the immediate shut down at 100% brightness behavior is resolved, the iFly software be set to have the default/startup screeen brightness be set at "Full minus one". The difference in brightness isn't that great, and we can always brighten it up and risk the immediate shut down if that's our choice.