Basically just did this again this week. I was re-reading a three year old board game design diary I had written, and came upon an old idea that I had put on the backburner after the prototype played just "ok". I tried to come up with ways to fix it for awhile, and the ideas I had then were so different they morphed into completely different designs (more specifically, it morphed into 1 different design, which bombed in playtesting, and then that morphed into a totally different design, which did really well in playtesting and I showed to publishers, and then reflecting on their feedback resulted in a completely new design sparking in my head).
I thought about the problem for a few more seconds, and one new thing to try popped into my head, not a totally different game this time still keeping with the core mechanism, but a different method how players were given and used the cards, and I dug into it a bit more, and I decided on a different method of point distribution for the cards, and then thought a bit more, and the thought of adding abilities that encourage comboing based one previous or next cards played popped into my head, and then I decided to run with it, came up with a new prototype, tried it out, and it felt at least three times better, and felt more like a game that could be published.
I have a game that is currently a finalist in a game design contest whose design had remained dormant for over a year because I was unsatisfied with it, but something made me think about it again and a new mechanism popped in my head and I tried that and felt a lot better about it.
The Feynman method works for me, at least when it comes to designing board games. I don't mind shelving game designs for a long period of time anymore, since I have had so much luck with just thinking about them again every once in awhile and fresh new ideas popping into my head to improve the game, that likely wouldn't have happened if I kept forcing myself to think about that game.