How do I know if an extra firm mattress is good quality?
Without testing a mattress it's quite hard to know what the quality is like, however, there are ways to curb this. Generally, you can rely on extra firm mattresses to not deteriorate as quickly as other mattresses due to the high tension they have in their springs already. Otherwise, it's a good idea to read the reviews and see how other people experienced a mattress and its firmness. The British Bed Company offer a 5-year guarantee with the Legend Ortho, suggesting it's of high quality.