Hi Hobo.
Welcome to our Mattress Forum. 
In general, we recommend avoiding reviews as a method of identifying a suitable mattress. People often review mattresses far too early after receiving them, and reviews lack specific information about all the variables that can contribute to the suitability of a mattress (like details about the person and the mattress) that would make them more meaningful/accurate. I’d suggest reading about the dangers of making a purchase based on reviews here. The same goes for review sites that more like revenue sites.
When it comes to the lifespan and durability of a mattress, your sleeping position, BMI, and activities on the mattress will also factor in. I recommend reading through our Mattress Durability Guidelines as well as these resources on different comfort layer types.
Ultimately, the longevity you get from this or any mattress will be determined by whether or not it’s an adequate match for your body type.
The Leesa Hybrid breaks down as follows (as per their website)
-1.5" Cooling premium foam top layer
DENSITY: 3lb IFD: 13
-1.5" Contouring Memory Foam
DENSITY: 4lb IFD: 12
- 1" Core Support Foam Layer
DENSITY: 2lb IFD: 30 - 6", 14.5 Gauge Pocket Spring
System with Perimeter Edge Support - 1" Core Support Foam Base
DENSITY: 1.8lb IFD: 32
For a person in a normal BMI range, our minimum density recommendation for polyfoam is 1.8 lbs and for memory foam, 4 lbs. Without knowing your BMI, I can’t speak to the appropriateness of this mattress for you, but as you can see, their foam densities do appear to meet the durability recommendations we suggest.
The Legend breaks down as:
1" Comfort foam exclusive to Legend (hole punched)
1" Pressure-relieving memory foam layer
1.5" Micro-pocket spring layer
1" Transition core support foam layer
6" 15 gauge pocket spring system with full perimeter edge support
1" Core support foam base
I hope this helps you in some way as you move forward in your mattress shopping journey.
NikkiTMU