When I was doing my Tool & Die apprentiship, one of the guys who was my teacher, shop Forman, and problem solver use to use a Gun cleaning patch between the measuring surface of his Microcomenters, and Calapers. When they were stored, just snuf in the jaws.
Reason was it kept particals or dust, dirt, etc., off the measuring surfaces. We were doing close tollorence work, sometimes within 1 or 5, 1/1,000th of an inch.
Back then a good Dial Calapers was like $75.00 or more, so you did not want to have to replace. It was almost a weeks pay.
Today for what you need, Calapers are cheap, just check the ZERO before each use, and you will be fine. Keep measuring surfaces clean with a soft cloth to remove dust, etc.