What is the best approach to maintain cookbook version for internal use - this is not public cookbooks.
With every new provision increase cookbook version - in that case new stuff are applied to the node
Work with single version of cookbook - on new provision delete the previous version and upload again. When there are same major features - then increase the version.
Follow semver and treat all cookbooks same way (public, private). It's just a good habit. Internal cookbooks may require rollback (sometimes) and proper version management as well as public ones. I don't see any reason for having single version except extreme laziness.