On Sizeable Shawls

I am currently knitting a shawl.  I have already sunk nearly two full skeins of Briggs & Little Regal (colour: Light Grey) into this shawl; am debating on whether I should end it here or crack into the third. Hm.
Reasons to go on: the pattern is simple, enjoyable and a classic.  I've got the chart happily memorized.  It's not irritating me in the least, and I've only been working on the thing for about a week.  The yarn is one of my favourites and is an absolute dream to work with.  And really, what am I going to do with one odd skein of the stuff (plenty of things, actually - at 272 yarns a skein its mileage is impressive).
I've just compared it to another shawl that I've recently turned out, and as it stands I could reasonably stop knitting this new one now.  It's completely functional at its current size and there's no shame in presently heading into the endgame.
But I do enjoy big shawls - shawls that you can wrap around yourself for days.  But this begs the question: can a shawl ever be too big?  At what point does it stop being a shawl and start being a blanket?

And then this image popped into my mind's eye:
Wear the shawl.  Don't give it the chance to wear you.

(And be sure to cast on another right away!)