As the technology sits now, 2 years is pretty good on horizontal surfaces, vertical will do better ( last longer )
I like those products that I recommended because they tend to fade and get lighter, making for easier maintenance. Many of the sealers available get darker with age, or fade somewhat blotchy requiring removal before reapplication. For me, its all about easy maintenance rather than longevity, because the longevity just isnt there. Many products will claim "X" year warranty...I havent found any that make it full term
Look around and read some reviews.