I think you are getting some bad info from your friend.
As far as reliability, see post #3.
Seriously, CJ's are at least 20 years old, they all have had several owners, many different types of maintenance schedules (or lack thereof), many different types of use, many years for things to get worn out. There are just way too many variables to make general statements like your friend has. Especially considering that the 1970 on up CJ's were made by AMC, which arguably was not known as a high quality era. I am not knocking the CJ, in fact I love them. The reliability of any older vehicle is dependent on it's maintenance and use history. As a general rule of thumb the older the vehicle the more maintenance it will require for many different reasons.
As the Jeep has developed over the years things have improved such as frame strength, fit and finish of the tops and doors, ride quality, etc. I have seen no such correlation between CJ,YJ,TJ and increased maintenance other than what can be attributed to the maintenance history and how the vehicle was used.
Sounds like you want to drive a Jeep and not have to work on it much, thats understandable. Then don't buy something old with an unknown history. I have a 48 CJ2a and that is high maintenance compared to my 77CJ5 I had which was high maintenance compared to my current 98 TJ. See a pattern there.