Absolutely not. If you have all that extra material, but are out of time, you lose. Sure, you could have won if you had a little more time, but if the time control were longer your opponent would have made better moves and you wouldn't have that extra material.
You benefitted from the time control earlier in the game when it induced poor moves from your opponent and your asking your opponent not to benefit from it now that you are out of time.
I just had a game of blitz in which I reached a very positive end game, (up two queens and a bishop) but by the time I got there I had very little time left on the clock. In this particular instance I managed to get the checkmate I required, but he must have known that I was going to win when his situation was so obviously bleak and yet he continued anyway, a tactic i'm dubbing 'the survival technique' - the mindset that rationalises: "Is it possible to just stay alive on the board until your oppenent runs out of time?"
Isn't there something a little unethical about knowing you are going to lose a game, but hanging on in the hope that you'll be "saved by the bell"??
Thoughts on this anyone?