I am developing several computational packages, mainly oriented towards control system applications. Several times I was confronted with keeping compatibility with earlier versions of Julia, where I set (I don’t remember the precise reason) version 1.2 as limit for backward compatibility. I wonder how much effort should be invested by the developers of new packages to keep compatibility with previous versions of Julia. For example, in my case, the DescriptorSystems package requires features (e.g., lower latency) provided basically only in Julia 1.6. The tests for Julia 1.6 takes about 20 minutes, while for version 1.2 they need 1.5 hours! For a typical concrete issue see #40586. So, should be any strong reason for me to enforce compatibility with version 1.2 ?
I would be pleased learning your opinions in this matter.