Long time observer of VJ here. I figure I'd chip in with my experience here.
Due to family reasons, I've been strategically pushing out my IR1 application (it's coming up on 2 years now since I received my initial case creation at NVC). For the first year, I pushed out my payments to extend the "keep contact" requirement.
Late last year, based on suggestions I gathered here on VJ and other forums, I submitted an "Ask NVC" inquiry simply stating that I needed more time to gather the documents necessary for my application but wanted to keep my case open. I got back the generic response by email that 1 year contact with NVC is needed to keep case active, and easiest way to do so is by accessing CEAC and it'll update the latest contact date.
Having an email from NVC on hand is insurance in case your case goes into termination and there's nothing to prove you've logged onto CEAC since there are no records.