I get delayed 75% of the time now. Never had a problem until 6 months ago. I went ahead and got 2 sets of prints and sent one to the FBI for a personal background check. Depending upon what pops up there, I'll either correct erroneous information or apply for a UPIN if necessary.
I've found that I don't get delayed midweek between 11-3pm. Friday late afternoon is a lock that I'm going to be delayed.
I wish I bought enough guns to know what time of day is best for a NICS check.