So I've got 2 uncomfortable beds at home: my main bed and the guest bed. I plan to modify them both but figured I'd start with the guest bed so I can learn from the experience. The guest bed is your basic minimal innerspring mattress with very little by way of comfort layers (the type you find in cheap furniture stores). We slept on that mattress for 5 years so hopefully the springs are in good shape (I must've used to sleep on my stomach during that time as the bed has very little give). If I find the springs in good shape I would like to add a comfort layer or two. My question is what would be a suitable comfort layer for a bed that sees only about 2 weeks of use spread throughout the course of a year? I don't want to spend hundreds on latex topping if I don't have to but I have to do something as the bed is really uncomfortable the way it is now.

 

Here are pics of the mattress. It is about 7 inches high.

To me the mattress looks like it is sinking and the springs are failing despite having no padding on it.  Maybe you need another inexpensive mattress for your guest room that will last longer if not many people sleep on it and you can buy an extra firm one and buy a 1" inexpensive Talalay Latex Topper.  Is this a Full or Queen size bed?

I see what you mean about the mattress sinking. I'll have to run a chalk line across it to see how deep the sink is. This is a queen mattress.

Just took a chalk line across the mattress in various directions. The measurements represent the maximum sink (in inches) in the mattress in that direction. Is it time for a new mattress?

I'll probably cut this mattress open anyway to see what's going on in there.