I am at 74' with my pickup, 5th wheel, and ProV in tow, and have been pulling doubles for 10+ years.
SD the length limit is 65', I believe anyway.
I have traveled all across ND pulling double, and a few spots in SD, I have never personally been stopped and measure, nor have I ever seen or heard of anyone else going through this process. Not sure on the fine, or any of that, but do not believe it to be one to lose sleep over.
I had a commercial license 20 years ago, and when it came time to renew my license I let it go cause it cost $10 more to renew. I said I don't need it anymore, the lady says "its only $10 more, and worth keeping". I said nope I need to save that $10 and wont be driving for hire anymore.... haha She says "If you don't renew it and ever want it back you will have to go throw all the testing and training all over again, are you sure you don't want to spend the extra few bucks"...
Needless to say I no longer have a commercial license, and those 3 beers at Chubs tasted like success...