Hi browser,
There is more about the pros and cons of wool quilted covers vs more stretchy knit covers in post #6 here.
Stretching or bunching of a cover generally isn’t an issue with a suitable mattress cover that fits tightly around the mattress components although mattress covers will stretch a bit and become a little looser over time. If it ever does become an issue over time then they can tighten the cover.
It also shouldn’t be an issue with the St Dormeir mattress protector as long as you choose the size and thickness that is most suitable for the thickness of your mattress.
There is also more about glued vs unglued layers and layer shifting in post #2 here but this also generally isn’t an issue because latex is very heavy and “sticky” and doesn’t tend to shift inside a mattress in normal use.
The covers also won’t hurt the edges of the latex.
The upper layers of a mattress are generally the weakest link of the mattress in terms of durability and are the layers where the quality/durability of the materials is particularly important. The regular deflection/compression of a foam material is what softens or breaks down foam over time and the softer upper layers of a mattress will deflect and compress more deeply and more often than the firmer deeper layers. Latex in general though is the most durable of all the foam materials so foam softening and break down will generally happen less and more slowly than with other types of foam materials.
There is more detailed information about the many variables that can affect the durability and useful life of a mattress relative to different people in post #4 here and the posts it links to.
As you mentioned … component mattresses with zip covers have the advantage of being able to replace individual layers if one of the layers softens or breaks down before the others (usually one of the softer upper layers) or if your needs or preferences change over time because you can just replace a single layer or component instead of replacing the whole mattress.
There is more about the pros and cons of thicker mattresses with more layers in post #14 here.
While your own careful testing or personal experience is the most reliable way to know whether a mattress is a good “match” for you in terms of comfort and PPP … when you can’t test a mattress in person then the most reliable source of guidance is always a more detailed phone conversation with a knowledgeable and experienced retailer or manufacturer that has your best interests at heart (which would include SleepEZ) and who can help “talk you through” the specifics of their mattresses and the properties and “feel” of the materials they are using (fast or slow response, resilience, firmness etc) and the options they have available that may be the best “match” for you based on the information you provide them, any local testing you have done or mattresses you have slept on and liked or other mattresses you are considering that they are familiar with, and the “averages” of other customers that are similar to you. They will know more about “matching” their specific mattress designs to different body types, sleeping positions, and preferences (or to other mattresses that they are familiar with) than anyone else.
Phoenix