Hmm. If one spends just 60 seconds on each, it would be a 6 month full time gig. Barely enough time to look at info/photos on Google maps and make a few quick judgement calls. Of course one could maybe reduce this of them by setting a threshold on their rating, maybe also number of reviews added last 12 months, etc. But yeah - lots of labor to actually evaluate thousands of anything. Months possibly.