Might be lazy, but with the price of DME, it makes sense. If it takes a pound of DME, which costs $5, to make a 4-L starter, and a smack pack costs $6.25 and is fresh, seems to me that the extra pack is the way to go.
Sound logic, assuming 1 extra pack is all you need.
I recently had a problem where I brewed 10 gallons of my regular light lager...
I pitched 2 Wyeast packs into each carboy.
One carboy took off well & one did not.
I ended up grabbing a large sample from the active carboy & transfering to the inactive one.
Then, fermentation kicked off, excellently.
While I give respect to Mr. Malty, I don't believe the calcs to be true.
They are drastic overkill, IMHO.
That said...I have obviously had problems with my Wyeast packs.
And, Wyeast is the only yeast with which I have ever had any trouble.
I can't blame storage, because Midwest Supplies has excellent storage practices & mine are at least equal.