Hi Diane37,
You will “go through” any topper to some degree because the topper isn’t the only layer that will compress so it’s more a matter of degree or “how much” it will compress. Both a thicker topper or a slightly firmer topper will isolate you more from the “feel” of the N3 below it but thicker/softer will have a softer overall “feel” and create a deeper pressure relieving cradle than a firmer thinner layer which will have a firmer feel on the sleeping surface. In other words … all the top layers of a mattress will compress to different degrees depending on the specific combination of layers.
The N1 would be more “resilient and “springy” than your 2” 14 ILD topper but the ILD would probably be close to the same and the thickness is also the same so if you aren’t doing well with the 2" Dunlop topper then a similar topper in Talalay may not be the choice with the highest odds of success.
My only caution with the 3" of 20 ILD (which would be a suitable layer based on “averages”) is that it would be fairly similar to the original N2 (which is somewhere in a range of 20 - 25 ILD) that you didn’t like and ended up exchanging (although as you mentioned you may have made the exchange a little too quickly). It would probably be a little bit softer than the N2.
As dn mentioned … it may also be true that you may do best with a less resilient layer on top of the latex in which case you may not prefer sleeping directly on any latex layer.
I think you’ve probably seen this but there is a list of latex topper suppliers in post #4 here. One of the advantages of buying a topper/layer from SleepEz is that they allow returns (less shipping) which is unusual. Sleep Like a Bear also has a return policy for toppers and Brooklyn Bedding has an exchange policy. Some of the others may as well but I’m not sure of the specifics. If you are uncertain about whether something will work for you then the return policy for a topper or layer may be an important consideration.
Phoenix