Mine's the same way too. Used to work, then one day, when I try to type in the rep box it disappears. Happens on my Xoom and Evo.
No longer easily possible in Texas since the introduction of electronic benefits and elimination of paper coupons several years ago.
If you invested $70 a month into a moderate risk fund or IRA and received a modest 5% return, over 10 years you would accumulate $11,600 (a total 40% net gain over your initial $8400 investment over that time). Over 20 years you would earn nearly $35k, more than doubling your $16,800 total investment. And all of this would reduce your taxable income every year. So yeah, $70 can be a lot of money.