ADD's
In my experience it depends a lot on for whom you fly and is directly related, in many cases, to the financial state of the company. Personally, it was uncommon to carry more than four or five ADD's and often they related to pax entertainment or galley problems. The worst I have ever heard of was a former PanAm L1011 which came in for heavy maintenance with a total of over 80 ADD's, some of which had been there for more than twelve months. Can't confirm the truth of the claim, however there was no reason for it to have been just a story.