I'll comment :P I would say just worry about what you haven't answered recently, then as you have time and if you have the energy, work on the back stuff. Honestly, it's always nice to get a little "thank you" for commenting, but it's not like I sit at my computer waiting for it. I comment so you can know that I appreciate something you've done, be it fic, or because you've been brave enough to share something personal and I want to acknowledge that. Is it good manners to go back? sure. But I don't think anyone would blame you for letting old missed posts rid.

*snuggles*