I did all the wiring myself years ago and was in a hurry when I did it.
I recently paid a qualified electrician to upgrade my service from 100 to 200 amps and it's all of course compliant to today's code.
Now that I'm retired I have sufficient time to go back over all the stuff I put in and do it right. The basement is all done now and though the attic *might* have complied to the code at the time, I might as well do it right.
To bring the stuff I did up to "current code" is going to cost me about $40 in parts, it's just my own time. As I mentioned somewhere else, I also want to be sure there is no chance a roofer will ever hit anything in the event I get a new roof.