After cleaning all of the preservative off and properly lubricating the thing, some regular cleaning should be performed. Reasons why:
1) A clean properly lubricated rifle will always be more reliable than a dirty one.
2) A clean properly lubricated rifle will always wear less than an dirty one.
And, most importantly:
3) You cannot inspect parts unless you disassemble, clean, and look at them.
Cracked bolts are a thing, it does happen. It is not a common as the internet leads you to believe, but it does happen, you should clean them and look at them regularly.
"But you can't see a crack." - Yes, you can. when the crack first starts, you can usually only see it through fluorescent penetrant inspection, but it will grow and become visible under medium magnification.
"If you can see it, it's too late." - No, The Army has done many endurance tests of more than 6,000 rounds on many hundreds of M16s and M4s throughout the years, and some do turn up cracked bolt lugs during the course of the test. Usually, the bolt is returned to service to see if and/or when it actually fails, rarely to they shed a lug before 10,000 rounds (if ever before the test conclusion).
"Isn't that dangerous?" Not really. In a test where bolt lugs were intentionally removed, a bolt with only two lugs (the bottom two, so it would feed), withstood 6 rounds before jamming in the closed position, and bolts with five lugs (missing the two flanking the extractor) when for nearly 1,000 rounds before the headspace exceeded the field gauge maximum, it did not fail catastrophically.
"I replace my bolt every 5,000 rounds, because that the life of the bolt." Well, how often you replace parts is up to you, and how deep your pockets are. But, the Army's average life of a bolt is well in excess of 5,000 rounds, some bolts do see cracks at 5,000 round, many more do not. So, if you clean and inspect your rifle at least every 1,000 round you should catch and problem before it becomes a safety issue. It doesn't have to be "white-glove inspection" clean, but functionally clean.
And one last thing:
Hopefully, you change the oil and oil filter in your car every 3,000 to 6,000 miles. The main reason is to remove the old, dirty, abrasive containing oil and replace it with clean oil, doesn't your AR deserve the same consideration?