Are my designs still useable for retail after my subscription has expired? Do I need to renew my subscription in order to continue the use of my desgins?
If you are talking about the CC, it depends on the format you need.
If it is AI, I am afraid you need to renew (unless you have downsaved to a version that you have (as perpetual licence)).
If it is PDF/whatever else, no need.
Your designs are your designs. Your files are your files. So sure, you can use them. Do what you want with them.
But if you need to open them or work on them, you of course need the software. If you're a Captive Creator, ya gotta keep paying to use the software.