What is the best practice recommendation for sending follow up surveys?

I always suggest to customers that they send one follow-up. We tried sending two when I sent out the surveys here (early 2015) and, while the first reminder pulled in a lot of additional responses, the second reminder garnered very few. So, it seems like it's not worth the effort and is just more noise to the customer. 

Here is an example time frame, if you want to leave the survey open for two weeks:
You send out your initial survey on a Tuesday (or Wednesday or Thursday, but not on a Monday or Friday)
The following week, you send out a reminder on Thursday telling recipients that the survey will close at the end of the day Friday. The idea is to give them a shorter timeframe in which to respond after the reminder, so they are more likely to do it on the spot.
You end the survey COB Friday

Hope that is helpful!