Nowadays, mattresses, for the most part, are "unflippable" due to memory foam and Latex organic mattresses being built one-sided. But is this a good thing?
Mattresses used to be made with two sides. I can't tell you definitively when they started being made with two sides, but I can tell you that some time in the early 2000's most major manufacturers started making them one sided. Now, many people have vilified the industry for this move, claiming that the mattress industry was just trying to make more money. However, the reason was simple: a house built on sand is unstable, and so is a mattress. When the bottom of the mattress is soft and squishy, the entire mattress rests on an unstable base, causing the top part to be unstable as well, leading to body impressions and layers shifting. I was selling mattresses at a furniture store at the time and one of the leading brands was having issues with body impressions, to the tune of about 20% of the mattresses we sold. It was not uncommon to field a weekly body impression in the mattress complaint. When they switched over to the single sided mattress, the problem almost dried up completely. Makes sense from an engineering perspective, but from a consumer point of view, it was understandable that the sentiment was you were getting half the mattress for the same price. But they lasted longer and were more supportive.
These days almost every brand builds a single sided mattress, and some of the more innovative, smaller brands, use better quality materials so you don't have to flip it to hide the wear. Think about it: you don't flip your car seats, and those are foam. Same with your couch. We have just been so conditioned to poor quality materials for so many years in our mattresses that we assume we are supposed to get a body impression in our mattress.
With a one-sided mattress, since you can't flip it, it's pretty much maintenance-free. That said, if you sleep on one side consistently, you will want to rotate the mattress, head to toe, at least once every 6 months. Some mattresses, such as organic mattresses with a latex layer, you can rotate or replace the latex inside the mattress. The latex and organic mattresses we have at Nest Bedding have zippers built into the top, allowing you to customize the feel and extend the life of your mattress by allowing your to replace the latex should it wear out over time.
So, in review, no, you don't have to flip your mattress, but it would be wise to rotate it head to toe every so often.