That's the only reason I joined such a site, the GS rewards. Normally I've never partake in these as they're mostly scams, this is one of the few who do give prizes without pyramid schemes.
It takes me forever as well. Which is fine since you can only earn them every few months and none of the other prizes are worth it. Surveys don't come often and I fail a lot of them when I don't qualify. Maybe I need to lie more, tell them I watch movies, use a cell phone, buy more beauty products, and so on. Only so much is checked in my profile because besides work and gaming I don't do much else. I'm still answering surveys based on a car purchase made 2 years ago, or insurance things when that isn't recent either.
Free is free though and I've earned 2 others with a third that just arrived last week (after redeeming it a few days prior). GS isn't my favorite store anymore, these would have been far more useful a few years ago. As long as they offer new games then I'll find something to spend it on.