A 1 year guarantee is a stamp of approval. You can buy with confidence knowing that if anything bad happens during that year of ownership that is the result of a manufacturing defect, you will be covered.
A 1 year guarantee is considered fairly standard for the industry. While consumers may agree that a larger and further reaching guarantee would ensure additional consumer satisfaction, the result more often than not is that problems in mattresses tend to rear their head in those initial 12 months, at which point claim drop off is typical across many manufacturers.