Chester wrote: None of the end grain boards have presented any problems, only edge grain (not sure what this means, but you guys that make boards for a living, tell me). I live in an 1800s house and in a very humid climate. When the AC is on, the house is dry, but when it is open, well, it is very humid. I am guessing that is one reason I have some problems with my boards.
Hi Chester, the short answer is it's hard to know for sure. I'll give it a guess. And the science of wood movement is something that professional woodworkers almost never agree on. We all have opinions, though.
First, I think seasonal changes in temperature and humidity are likely the culprits, as you suspect. Rubber feet allow air to circulate around the board equally, so that should reduce the impact of exposure to the elements. But that's still my best guess. Another possibility could be if you always oil the top but never oil the bottom of the board.
I think I can explain why end-grain boards don't often warp (if they are taken care of). First, the end grain blocks are generally around 1 3/4" squares (some manufacturers use bigger blocks, granted). In theory, wood that is milled into smaller pieces will be under less tension, and less prone to bow, twist, or cup over the years. I have no doubt that people will disagree with me on this point, but that's the main reason that I've avoided using huge blocks of wood in my end grain boards. It takes more cuts and more time to use smaller squares, but I think it will be slightly more warp-resistant over the decades. Second, if end grain blocks expand or contract, they will do so in tiny amounts, and they will do so laterally. An exaggerated picture of this would be the entire length and width of the cutting board growing or shrinking slightly with changes in temperature and moisture. So the size of the board is changing, but it's staying flat on the counter.
A face or edge grain cutting board, on the other hand, is normally built up of big strips of wood laminated together. When humidity changes. Those can swell or shrink in a number of ways, resulting in cupping, bowing, twisting, just like happens to the hardwood lumber sitting out in my shop. Unlike the lumber in my shop, a face grain cutting board is constantly getting bombarded with moisture and humidity. So that's inviting those inner tensions in the wood to be released.
But... all that could be gibberish. It might just be that you are being sent a divine message that you need to buy a new end-grain wood cutting board.
FWIW, our kitchen island is end grain maple, and we cut on that most of the time. We also have a face grain walnut and maple board, and both have stayed dead flat over the last 5-6 years. The funny thing is the island shows very little wear and tear (other than where my 4 year old repeatedly hammered an ice pick into it). The face grain board, on the other hand, looks like it was in a terrible knife fight and lost.