The geocoder has quota and rate limits. From experience, you can geocode ~10 locations without hitting the query limit (the actual number probably depends on server loading). The best solution is to delay when you get OVER_QUERY_LIMIT errors, then retry. See these similar posts:
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OVER_QUERY_LIMIT in Google Maps API v3: How do I pause/delay in Javascript to slow it down?
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How do I Geocode 20 addresses without receiving an OVER_QUERY_LIMIT response?