FYI From the Terms and Conditions:
"The Samsung Visa® prepaid card is not redeemable for cash at any ATM. Terms and Conditions apply to the card. Subject to applicable law, a monthly maintenance fee of $3 (USD) applies, but is waived for the first six months after the card is issued. Your card is issued by MetaBankTM pursuant to a license from Visa U.S.A. Inc. Cards can be used at any merchants that accept Visa debit cards. Samsung reserves the right to substitute a check of equal value in lieu of a Visa prepaid card at its discretion."
$20 is still $20, but you should be aware of this before you jump in.
I don't know why you'd hang on to the card for more than 6 months, but If you do, you'll lose money quickly.