Hi Peachy,
The quality and durability of the materials have nothing to do with whether how a mattress feels or how supportive a mattress will be or whether any mattress will be a good match in terms of PPP (Posture and alignment, Pressure relief, and your own Personal preferences) … only with how long the mattress will maintain it’s comfort and support over time.
While there is no way to quantify how long any mattress will last for a specific person or predict exactly when you will decide to replace it because it is no longer suitable or comfortable for you (because this is the only real measure of durability or the useful life of a mattress that really matters) because there are too many unknowns and variables involved that are unique to each person … if a mattress is well inside a suitable comfort/support range and isn’t close to the edge of being too soft when it is new (see post #2 here) and you have confirmed that it meets the minimum quality/durability specs that are suggested in the guidelines here then it would be reasonable to expect a useful lifetime in the range of 7 - 10 years and with higher quality and more durable materials like latex or higher density memory foam or polyfoam (in the comfort layers especially) it would likely be in the higher end of the range or even longer and the chances that you would have additional “bonus time” would be higher as well.
In other words (and without attaching a specific number of years which isn’t possible) … it would be reasonable to expect that the the Helix could be in the lower end of the range while the BME would likely be in the higher end of the range.
Phoenix