Hi tomato,
If by “natural” you mean the blended Talalay latex (compared to the “all natural” Talalay which is 100% natural latex) then there is more information in post #2 here (about natural rubber vs synthetic rubber) and in post #2 here which compares the two types of Talalay latex.
Latex International (which owns Pure Latex bliss) also mentions here that their blended Talalay will last longer than their 100% natural Talalay.
I would always suggest a mattress protector yes. It will keep the sleeping surface more hygienic by preventing body fluids and skin cells from getting into the mattress (and feeding the dust mites) and it will also protect the warranty which is usually voided by even a slight stain on a mattress. Post # 89 here has more information about the different types of mattress protectors and the tradeoffs involved in each.
You can read more about the many factors that are involved in the durability and useful life of a mattress in post #4 here. A topper will generally extend the useful life of the layers below it yes and can be easily replaced without replacing the whole mattress but the down side is it can be more difficult to choose a topper that is a good “match” for a mattress and the person sleeping on it unless you have the chance to test them together (the mattress under the topper will be a big part of how a topper feels). Better quality and more durable toppers will last longer of course than lower quality toppers. If the comfort layers of a mattress use high quality materials then they can also last for a long time with or without a topper. The upper layers of a “sleeping system” are generally the weakest link in the mattress or sleeping system.
Good quality toppers are usually heavy (such as latex or memory foam) and if they are under a mattress protector and sheets they don’t shift much at all and if for some reason they do they are easy to re-position.
Pure Latex Bliss mattresses use high quality durable materials (latex) and there is no reason to avoid them if the mattress you are considering is a good match for you in terms of PPP and is the best value available to you in terms of your personal value equation. Regardless of which manufacturer uses it in their mattresses … latex is a high quality and durable material.
Most latex allergies are a contact allergy and are to different types of latex products such as dipped latex (including gloves, balloons, condoms, medical equipment) which are different from foamed latex latex which has had most of the surface proteins washed away. This is by far the most common type of latex allergy (and isn’t actually an allergy although most people call it that) and a latex mattress would be fine for these people. People who have a type 1 latex allergy on the other hand (which is rare but can be very serious) should avoid any contact with or proximity to natural rubber in any form. There is more about latex allergies in post #2 here.
Phoenix