For daily use on the Isle of Man, watch the condition and support of the futon rather than planning replacement solely by age. The owner's three-to-four-year reference describes a cared-for nightly routine in Japan. It cannot establish how long a different room and user will find HIMARI or SORA comfortable.
What does regular care help with?
Airing and dry storage address moisture, while turning and rotation change where pressure falls. They do not keep new loft unchanged indefinitely. Fibre materials settle, and airing cannot permanently rebuild filling that has compacted through years of use.
What should I check before keeping it as a spare?
Inspect both faces and decide whether it remains clean, dry and comfortable for that use. Check it again after storage. A futon with mould should not be placed underneath a new one or kept for guests as a way of overlooking its condition.