I was about to ask how long these are good, then actually looked it up - on one of the certificates. I'm happy to see that it's a year "except in California". Cooool...

Unfortunately, I'm not seeing any overlap with RewardsNetwork. (How much can a restaurant "give back" at once to promotions?) Though some do also participate in OpenTable, making possible the 2,000 OpenTable point $20 promotion -- unless the combination can be detected and noncombineability invoked.