Good Evening John, 
 
Thanks for your question. 
 
Ultimately - The answer is yes. You need to utilise the whole sleep surface. If you're sleeping on the sides of the bed then you're compressing the mattress on those sides but not the middle meaning that you end up with a raised ridge in the middle. Many people fall into the trap of thinking that this is the mattress failing but it's not. It's simply a case of you need to sleep across the whole surface. 
 

 
Please see the link here for our advice on correct maintenance and care. 
 
I hope this has answered your questions fully but if you do have any further queries please don't hesitate to contact our office on 0161 437 4419. We are open Monday to Friday 8am to 8pm and Saturday and Sunday 10am to 4pm.
 
Kind Regards, Lee.