Digital feedback channels don't necessarily work with your best clients.
Why?
Because your best clients already interact with your business on the regular. Why would they fill out an online survey?
A feedback survey may be good for a new client. Someone who doesn't already have a long standing relationship with your business.
For your high-value clients, the feedback mechanism has to be different. Because how they work with your business is different. You already won them over.
Sometimes a simple phone call gives you solid feedback. Other times, a chat over in-person coffee leads to great conversations. You better believe a round of golf is going to bubble up some comments.
Their feedback is gold but you have to rely on different techniques than an online survey.
 Client feedback is incredibly important as you want to grow your business and improve your client relationships. However, a lot of your best clients don't fill out those formal surveys that you send them. And I know it's like, "Man, if they had just filled it out, we'd be done by now!"
However, think about a Yelp review. A lot of people that leave online reviews are usually because they had a negative experience. But with your best clients, they may not have a negative experience, so why would they leave a feedback review? They may say "things are great". And what you want to be able to do is take their quote of "things are great", and really dig down into why are things great.
Whenever we want to get feedback from our best clients the best thing to do is pick up the phone and call them, sit down with them, have a cup of coffee, and ask those questions to them face to face. Get their stories out of them, and don't just rely on a digital survey feedback for them to give you "your company's doing great" response.
What you want to hear and dig into is "That person I worked with on that last project was stellar and I have six more projects that I want to work with you on." That feedback may not come out in a survey. They may look at that emailed survey and think "this doesn't apply to me because I'm already a best customer and they already know my stance on it".
Really take the time, do some one-to-one and personal feedback conversations, and it'll open up your eyes to how your best clients actually perceive your company. You'll be able to get so much more data and information out of them rather than just a simple feedback form.