How to view my posts and responses on official Apple Support Community website?
After you sign in, the main Welcome screen displays. Here's a screenshot of the top right portion of that sreen:



At the top right, select "My subscriptions." That should return a list of the threads to which you're subscribed, and I think one is automatically subscribed to threads one starts.

I don't know if subscriptions (or their listings) are automatically cancelled after a period of time.