i've yet to get a single location based one, tho a friend who doesn't ever remember to open the app got 3 of them just 2 days ago
There could be other factors, too, like whatever demographic options you indicated when initially signing into the app. I think I got asked this question again a year or so later. A lot of traditional surveys (and on ones like Amazon MTurk) will also filter out people based off of where they place in whatever demographic section of whatever group they're testing for -- only MTurks is like slave work considering:
1) It takes a long time to build up a good reputation to get to the "better" surveys
2) You literally spend hours of time on surveys that may be only worth anywhere from 50 cents to 2 dollars
3) You sometimes have very anal reviewers who can screw over your rep because you answered one question out of a hundred incorrectly.
Google Opinion Rewards is a stress-free, relatively passive alternative to making small change that accumulates (trickles in) over time.
It also depends on where you go. Any major chain I'll usually get one for, like Meijer, Target, Best Buy, Biggby, Starbucks. After a while, though, they start to disappear (for whatever reason). Whether it's testing your trustworthiness, testing their location accuracy, or whatever other purpose it's for, which is why I'm thinking it may have been better for early adopters. I don't get Meijer ones as often (or anymore, I don't think).
You also get a ton of surveys if you own a small business.
Do you get a warning when your credits are close to expiring?
I've never gotten a warning but it's been long enough where I'll think, "Shoot, maybe this will expire soon." So I'll spend a small chunk of it to be on the safe side. I think for other promotions, like when they had the ~$20 free Google Play credit for buying a Nexus 7, I've gotten an email reminding me of its upcoming expiration.
