Most will say no. There is no true "savings", you get vouchers and if you plan carefully you won't loose money.
Example: Purchase a $8.99 meal. Use a $5 voucher and pay the difference. If you only have $10 vouchers left, you will NOT get change back.
If you want to pre-pay for meals, put that $$ on gift cards which can be used at almost all places in DLR.