If you use Rogaine for traction alopecia, you wouldn't have to use the product for life once the hair grows back—correct?

To some extent yes. It depends on the severity of the alopecia, but rogaine can at least in part help to undo the effects of it. However in most cases it is impossible to return the follicles back to their original healthy state completely. But yes, if you stop rogaine later on and treat your hair more gently it probably won't regress. These are all generalizations though and so it's possible for any specific case that some or all of these assumptions aren't true- a hair loss specialist can help determine if you fall into that category.

You are correct - in part. If your traction alopecia has gone on "too long" (meaning many months), the hair follicle CANNOT completely heal. Therefore it can not completely regrow. However, if the traction has gone on a few weeks, the potential is there for complete healing. IN this case you are right, you can stop Rogaine and the hair will still keep growing. Traction alopecia is often not completely regrowable if the damage has gone on too long.