Hi withgiants,
since it sounds like with or without the redirect on the withgiants.com domain anyone going there would get an error.
That's correct, once the domain expires, then any links to the domain will stop working (and it will eventually become available for someone else to register). Like I said though, you can keep the redirect on withgiants.wordpress.com if you'd like, as that will still point people to garynealhansen.com for people who go to withgiants.wordpress.com; you don't have to do anything special though, that redirect will continue to work without you doing anything.