Recommendations for some decent calipers...

I use mine like you, nothing vital, and purchased a set of digital calipers off eBay a couple years ago and am very happy with them.

I only buy Mitutoyo now. They are the best and the batteries last for years, even with daily use. Yes, they cost more, but they are worth it. I only buy the "absolute" coolant proof IP66 models. I have 6 digital calipers in various sizes, because I often misplace them and I hate hunting for tools!

Midway USA has some decent quality calipers both digital and dial. I prefer the dial and I've owned mine for many years and trust it's accuracy.

https://www.midwayusa.com/calipers-and-micrometers/br?cid=8866

So, I've been using this Harbor Freight set of calipers https://www.harborfreight.com/4-in-digital-caliper-63710.html for about 10-12 years with no issues. At $15, it's been accurate and repeatable enough for what I need to do. 

I've had harbor freight for years. The newer ones are quite rough, my original set as smooth as the mitutoyos at work. Batteries don't last long...but are cheap on Amazon. LR44/357 type. 

Measure just as good as the mitutoyos at work. I need to have our calibration guy calibrate them...