You'll never get real sales feedback from your customers except lost deals. But then it is too late.
Your customer will not tell you what your problem is.
I can because I have been doing this for 17 years, from a sales rep to several senior executive sales roles. Stop spending months of iterating your sales approach as the risk is to high that you have lost your most interesting customers by then.
Reach out to me when you are ready for some real sales feedback and want to accelerate your sales: email@example.com