Mobility-Still the Holy Grail

Mobility is key to the "quality of life" everyone talks about when referring to their career. Divisions between work & personal life are fuzzy. You are key to your team and even though you left things to a capable deputy while you are on vacation, do you return the email sent to your work email at 4:45PM EST when you are +3GMT and it is almost 1AM and you are still dancing your bootie off on your cruise? Tough...alot of us want to be that accountable but to what extent is acceptable now that these boundary lines are so blurry? Does the ettiquette exist yet? Who says which is the right way to go about things? It's not like sizing up your salad fork!