Should my mattress always have a guarantee? The short answer is: yes, of course you should get a guarantee with your new mattress. A new mattress represents a significant investment, and should last you many years. If your new mattress does not come with a guarantee then you should not buy it, it is simple as that. You should not buy from any manufacturer or retailer who will not stand behind their product.
You guarantee should cover a number of different areas, such as replacement, repair and return. Most of the time, a manufacturer will replace you new mattress within the guarantee period if there is any significant defect in either the workmanship or the materials. For example, if there the filling is poorly distributed or settled, if there is any discomfort caused by poor workmanship, instability or damaged ticking.
In some cases, the guarantee may cover repairs as well, though there will often be costs associated with transport that you may have to cover. Generally replacement is the preferred option for customers, so check your guarantee to see under what conditions repair is considered.