Never before and while stocks last

I WONDER if any one has the same problem when writing an ad with the phrase "While stocks last". Should it be "While stock lasts"?

I was a copywriter with a small advertising department of a retail company. As it was selling mostly electronic goods, there were many ads which required "While stock lasts" or "While stocks last" (in 9-point light at the bottom of the ad, after an asterisk, or sometimes in reverse white as a diagonal strap at the bottom right hand corner).

I thought "stock" may be used generically, hence it can be used in its singular form -- you know, like the use of the word "fish". But then, my predecessor had always used "While stocks last". My boss, who was the general manager overseeing retail and marketing, didn't really care much as long as I have the statement in all the ads. So I gave a call to my friend who was working as a reporter with the newspaper. She said, "Hmmm, I think 'while stock lasts' sounds more right."

So I requested the graphic artist who laid out the ad, to change it to "While stock lasts". After a while, I asked myself, what if the ad was shouting more than one kind of item "up for grabs" (which was often the case). So there would be more than one kind of "stock" and so it should be "stocks" (like fishes). So the poor graphic artist was requested to change it back to "While stocks last".

While "while stocks last" or its singular version was a variable in the ads that I did, "Never Before!" (with B in caps and an exclamation mark) was a standard. My boss insisted. Though he didn't spot the "stocks" or "stock", he never missed "Never Before!".

"I think add "Never Before!".... people will sit up...Put a burst here," he would mutter each time I showed him the mockup.

"Or how about 'Exclusive Offer!' for the burst? Hmm, never mind lah, 'Never Before!' sounds better,"  he said after some consideration.

There was just one time when I couldn't bear to put the line "While stocks lasts" in the ad for a rather classy handphone -- and my boss said, "Better add 'while stock lasts'..."