In many, if not most, disciplines methods age, get old and eventually become more or less obsolete, in the sense that some other method perhaps using a different technology becomes common-practice for a particular type of experimentation. One such example could be Edman sequencing, which used to be the method for sequencing peptides, but is pretty much outdated nowadays, not because it does not work, but because it's costly in time and labor.
In my experience, these old/obsolete techniques are taught both at Masters and PhD level, primarily to give a deep understanding of the field, albeit being more theory than practice. Are there any other benefits in learning/studying older methods, rather than only studying the state-of-the-art?
I was wondering how often, if at all, such old methodologies come back (perhaps following a breakthrough in overcoming some original limitation) and regain popularity. Are there known examples?
As a follow-up; is such change in methodologies a phenomenon observed in experimental research, or are there equivalent scenarios in theoretical research as well?