What is the criteria for the full time rateing? The Army rated their field tents as full time because they could. To me it is marketing ploy or maybe a method to not warrent an RV if they don't rate it as full time.
I would view the "criteria" as you getting your warranty problem fixed after explaining to the dealer, and perhaps to Heartland, that you live full-time in your RV. As Jay said, we've never heard of any full-timer getting turned down for warranty, even on models where warranty doesn't support it. While that's a good indicator, it's not a guarantee of what might happen in the future.
By contrast, you might want to search for and read the warranty statement for competitors like Keystone, where "residential" use causes the warranty, in their words, to "not apply". Interestingly, the Keystone Montana sales brochure claims a full-time warranty, even though the actual Limited Warranty excludes it. Maybe their documents will get in sync soon. If I was considering a new RV for full-time use, I would be a lot more comfortable with it being supported in the Limited Warranty. The brochure statements are always subject to change without notice. No so with the Limited Warranty. The Limited Warranty provided with the purchase is the one that counts.
I just ordered some work to be done by Home Depot where the sales pitch promised a very comprehensive, very competitive, wonderful warranty. However, when I asked for the actual warranty documents, it took them 2 days to find them. And the Limited Warranty documents were at odds with the sales pitch. I asked for 5 specific promises from the sales pitch, that were excluded in the Limited Warranty, to be written into the sales contract. They about had a cow, but got permission from HQ to do so. My view was that a few years from now, after all the current people are gone, there's no telling if the new Home Depot employees would respect the sales pitch details. But I'm comfortable they will have to respect the sales contract. I doubt my Home Depot approach would work with RV sales, but my point is that the language in the sales pitch/brochure isn't worth much in my opinion.
And in my opinion, counting on coverage that is excluded in the Limited Warranty is risky.
So to me, the Heartland Limited Warranty language supporting full-time use is pretty significant.