Hi davess,
There is more about the pros and cons of a “finished mattresses” that generally has glued layers vs a component mattresses with unglued layers and a zip cover in post #15 here and post #2 here.
I would personally leave the layers unglued so that you keep the advantage of being able to replace individual layers without having to replace the entire mattress if one of the layers softens or breaks down before the others (generally the top layer) or if your needs and preferences change down the road. While your layers may shift slightly with ongoing use over time or when you move the mattress … if this happens it’s a simple matter to open up the cover and “wave” them back into position again (without pulling or tugging which can tear or rip the material) so IMO the advantages of the unglued layers would be worth the tradeoff.
Phoenix