If you ever intend to challenge the Kanji Kentei, they are a section of the exam beginning with level 4. I learned about six hundred of them through the course of studying for level 2.
There are some that are widely known and used, but for the most part they will whiz right over the heads of native speakers of Japanese just as high and fast as they do over the heads of foreign learners. Absolutely bloody useless things for daily use.
If you see or hear one used, learn it if you like. The fact that somebody else used it means it is likely in general use and will be understood.
Here's the problem:
If a native speaker drags an obscure one into conversation, people may think he is just super-smart and using something they don't know. If a foreign speaker drags an obscure one into conversation, people just assume you are mangling something else and will lump it in with all your other mistakes.
Learn them if you have to. Learn them if you want to. Just don't expect to get a whole lot of mileage out of them.
こんにちは！Hi Everyone. This is a site I built to randomly show a yojijukugo(4 character idioms) as well as show the correct way to write the Kanji. I would be interested to hear from anyone if they spot any mistakes etc. I don't make any money from it, just a personal project.