If T-cell count and function is normal immunity should last. The idea that immunity wanes is coming from universities looking at antibodies (a different immune cell) as markers for vaccine efficacy. Industry prefers that way because waning antibodies means they'll sell more "boosters"

You shouldn't be down voted. This is mostly correct. Cellular immunity is durable in most recovered patients. People can expect to get reinfected occasionally but subsequent infections typically have less severe symptoms.

Boosters are a good option for many people (talk to your doctor). But using antibody levels as a basis for scheduling boosters is completely unscientific. As a society we can't boost our way out of the pandemic.

This panel discussion with a group of leading physicians goes into more detail on the issue.

https://youtu.be/jAjKQY0_BQA