Maybe, but I suspect it could last up to a few more years - replacing it will ensure you avoid the hassle of it dying unexpectedly.
I am not surprised it has lasted this long. High temps kill lead acid batteries as well as lithium ion cells (though I suspect to a different extent at the same temp). I found in my Volvo V70 (battery near rear bumper) and BMW 328iS (battery near rear bumper), I got 7 to 8 years of life before needing to replace them. On my wife’s Flex, battery is in the engine compartment (super hot area) and it needs to be replaced every three years.