I want to share the following with you, because it happened to me.
I heat the shop during Winter, using a forced air system. This creates a very dry heat that could result in bench tops not being as flat as we might need them. The following photos illustrate the current status of my workbench top - the total gap in the top photo is 1/8-inch, with the precision straight edge held flat on the back edge of the bench:
The bench top:
The end cap:
Of course, the dry air is likely to also affect everything else wood in the shop, such as your lumber and, by extension, any projects you are currently working on.
I recently bought a monitoring system, which will allow me to monitor the relative humidity in my shop using an inexpensive hygrometer that also monitors temperature. I believe I will be able to start using a humidifier when needed, to attempt to keep the humidity in the shop fairly constant.
You will find additional details and comments at my blog.