Hi Edna,
 
Thank you for your question. I am sorry to hear that both you and your husband are suffering on your 15 year old Tempur mattress. Memory foam usually starts to dip and sag after a few years so the fact that yours is still in good condition after 15 years is very good.
 

 
Memory foam is notorious for heat retention as it requires both body heat and pressure to be able to mould to you. This heat does not dissipate but it fed back to you making you overheat.
 

 
The pain in your ankles and your husband's back pain could indicate that the mattress is now too firm for you.  You do not say how you sleep but if you are a side sleeper and you cross your ankles in your sleep this would put added pressure on your ankles if you do not sink in enough. If your husband is a side sleeper and he is pivoting on his shoulders and hips, this puts pressure on the lower back.
 

 
Adding a soft-density Latex mattress topper would provide you additional comfort and allow you to sink in more. 100% natural Latex is much more breathable than memory foam and it only requires pressure to be able to mould to you. I would not recommend a medium density given your light body weights. Unfortunately, we do not have a soft density latex so I would recommend a company called Latex Sense which has a wide range of mattresses and toppers available.
 
I hope this helps and if you would like any further information or would like to discuss your individual needs, please do to hesitate to contact the office on 0161 437 4419.
 
Kind Regards
Michaela