Considering buying a latex mattress but the one I looked at has only a 1 and a half inch comfort layer over a 6 inch core. Is that layer too thin? They have another one and a hlaf layer on the bottom. I noticed most have at least a 2 or 3 inch comfort layer.
I suspect the mattress is constructed in that fashion in order to allow it to be flipped. I think that’s an advantage, and one regret about the mattress I bought is that it’s not made to be flipped. That being said, I think 1.5" of a comfort layer is a bit on the thin side, but the reality of that situation would be impacted by things such as your body weight and sleeping position(s), etc. For some people it might be fine, for others, not so much. I have a mattress that amounts to the same depth as yours, but it is made of a 6" support layer and a 3" comfort layer. Given my 'druthers, I might wish it had a 3" comfort layer on each side, but then I’d be living with - and trying to find bedding for - a 12" mattress, which would be a bit much for some people.
I’m sure Phoenix will be along with a better answer. The thing that I’m sure of is that personally I’d not want a comfort layer that thin, but I’m not willing to go so far as to say I think that by itself would make it a “bad” mattress.
What about the notion that flipping is important? Does it really matter with latex? We also bought a 6" core + 3" comfort layer. I thought that if I really need to flip it, I can unzip the cover and flip the individual layers. Does this sound silly? I would love to hear from someone who has been sleeping on a latex mattress for >5 years…
Hi adler223,
That would depend entirely on the specifics of the top layer and the other layers and components in the mattress.
If you were a side sleeper for example you may need the top 3 or 4" of the mattress to be fairly soft to relieve pressure points (regardless of the thickness of any individual layer) so you may need a little softer support core which can “help” the top layer relieve pressure. If you were a stomach sleeper that was more concerned about your pelvis hammocking into the mattress and causing back and alignment issues then you would probably need less softness and the 1.5" over a firmer core may work fine.
One of the goals of a mattress is that the pressure relieving cradle that contours to your body is deep enough to relieve pressure for your body type and sleeping positions and the thickness and firmness of the top layer and the softness/firmness of the base layer all contribute to this.
Post #2 here has some links to some of the concepts and theory about how different layers and designs can work for different body types and sleeping positions but all the layers and components in a mattress interact and affect all the other layers and the best way to know whether a design works well for you is by careful and objective testing for PPP (Posture and alignment, Pressure relief, and Personal preferences) following the testing guidelines in post #1 here.
There are no “layer thickness rules” … only the combination of materials and components that works best for each individual person.
A two sided mattress will also be more durable than a one sided mattress as long as it’s regularly flipped and rotated … even with a material that is as durable as latex.
Latex is a very durable material even in a one sided mattress. Some one sided mattresses also have individual components or layers that can be flipped or rotated or even replaced that can also extend the life of the mattress and some “sleeping systems” have a base mattress and a topper where the topper can also be flipped and rotated or replaced which can also extend the life of the layers or the mattress.
While any one sided mattress will be less durable than a two sided mattress in an apples to apples comparison that uses the same materials … they have the advantage of being able to use more complex layering designs than two sided mattresses because you can use thicker or multiple layers of softer foam on top of a firm support layer in a one sided design that isn’t possible in a two sided design because you would have too much softer latex on the bottom which would be a risk for support and alignment issues.
Everything has a tradeoff 
Phoenix