Hi cado2012,
With a manufacturing date of 2012 … it’s not likely that the mattress is either new or that it has a manufacturer’s warranty (see their page here which says “Products do not come with warranties”. I would also keep in mind that a warranty only covers defects in a mattress and not the gradual (or rapid) loss of comfort or support that is the most common reason you would need to replace a mattress. The length of a warranty is never as important as knowing the type and quality of the materials in a mattress and that it has little to do with the quality or useful life of a mattress (see post #174 here). You could always check with Restwell to see if they are an authorized dealer and if they were then they would almost certainly have a number of current Restwell mattresses on their showroom floor.
As you probably know from your reading here … Sleep EZ would be a great quality/value choice and a component latex mattress has the advantage of having many options to customize your mattress both before and after a purchase either by rearranging layers or exchanging a layer.
When you can’t test a mattress in person then the best way to choose which mattress would likely be best for you would be a more detailed conversation on the phone where they can help “talk you through” the options they have available that would have the best chance of success based on the averages of other customers that are similar to you (see mattress firmness/comfort levels in post #2 here). Any local testing you have done on different latex mattresses that use either Dunlop or Talalay in different firmness levels so you have some sense of what latex feels like in general and which type of latex you tend to prefer would also be useful.
Phoenix