> Money is money. Since you can use it any time you
> please, why not use it when you have the greatest
> chance to win the hand?

> If the bet is insignificant to you, and you really
> don't care, then play it whenever you please.

> Don

I had wondered about that too. Looking at Norm W.'s "Blackjack in Color" charts,Chapter 2.5,it appears that the percentage of hands won is practically independent of the count in the normal playing range of, say, -2 to +6.
However, from +2 up there is a slight decrease in loss percentage, balanced by an increase in pushes, which would allow you to use the coupon again - a very small gain if it's worth waiting for.
There might be a disadvantage in waiting for a good count too. If the coupon counts as part of a table max bet and only gets paid 1-1 on a natural, you would be better off betting that max in chips.
For small coupons worth table minimum or less, I've decided to use them in neutral or low plus counts. If the coupon value is significantly more than table min, I would wait until the count justified the matching bet.