Hi John,
We only provide mainframe access when it's associated with a course, and those courses have an access time of a few weeks.
Additionally, access to that mainframe is only to be used for the purpose of that course, so if someone were to sign up for the Mainframe Practitioner course, which gives them access, and they start compiling a bunch of programs, their account will be terminated.
If you want persistent mainframe access, you should talk to someone in the community at Open Mainframe Project or look into ZD&T.
https://www.ibm.com/products/z-development-test-environment