That seemed odd to me as well (also diabetic). When I'm not being responsible, I can ride out a BG of 300-400 for hours and mostly I'm just lethargic.

That said, my mother in law, who had worse diabetes than me, went without her pump during mine and her daughter's wedding (a bit of vanity about the pump showing through her dress). She was at 600+, and started feeling pretty ill that evening.