The problem is that all of these techniques are based on speculation and/or empirical data, but without solid measurements, especially since google's ranking system is a black box. Personally I have encountered 2 opposing opinions on this subject, one suggesting that google does take the duration of the registered domain under consideration, based on some patent that google had filed about it's ranking system, and the other one was from some supposed employee who claimed it didn't, due to the fact that some registrars withhold this information and thus no comparison could be made between them and domains on those that publicized it.