I Loved my Futon but it Became Flat
When I was younger I moved around a lot and I found it really helpful to sleep on a futon, because I could roll it up easily to transport when I moved. It was also healthier than many of the mattresses out there, made of all cotton. I didn't really like sleeping on metal coils!
In those days futons were just made of cotton, so after a few years it became quite flat. I didn't mind, at that time I was young and didn't really notice it. Since then I've learned that a futon needs to be refreshed every once in a while, by bringing it outdoors and shaking it out, which fluffs up the cotton again.
Nowadays there are lots of new types of futons out there, that have foam or even coils to help them maintain more of their springiness. I haven't tried these, but I would recommend if you go that route that you try a regular futon with a latex mattress topper
Although latex is much more expensive, it is very comfortable to sleep on, is hypoallergenic (if you are not allergic to latex of course) and resistant to dust mites. Latex toppers are also quite comfortable so you won't notice if your futon gets a little flat!