Wet cell batteries die due to the fact that as they cycle (i.e. discharge and charge) they slowly build sulfite's on the lead plates through the electro/chemical action, slowly reducing the transmittable area that the lead cores can take up a new charge.
Most wet cell batteries have 6 plates and cells, the longer lasting batteries ( 7 and 8 year warranty)use a thicker plate and a slightly diagonal grid design to give them more of a usable surface area. That is why the cheaper ones are lighter, thinner core plates.
Although Optima uses a medium size plate its there spiral design that gives it a much larger surface area than wet cells. Plus the more expensive gel.