AGM, EFB and SMF (sealed maintenance free - conventional) batteries are all marketed as having different design and properties. In order to justify the cost differential of 50-100% extra compared to SMF, they all claim their batteries are good for xxx start stops. So logically the lifespan should be longer and a longer warranty given. But no no, the warranty period for AGM, EFB and SMF batteries destined for all gasoline engines is the same.
To make an AGM or EFB worthwhile, it must last 1.5-2 times as long as a normal SMF battery, because these batteries cost this much more.
If installed in a normal non start stop car, AGM batteries must last at least twice as long as a SMF battery. This translates to around 4-6 years lifespan, since a normal battery only lasts 1-3 years in a normal car. In actual fact, even normal batteries can last 4-6 years in a normal petrol car. But its very rare.
Conversely, when a normal SMF battery is installed in a start stop car, its life span should be shortened. But in real life, the life span of a reliable SMF battery does not differ much from an AGM or EFB battery. This is something u can test out yourself.
So in real life, AGM and EFB batteries do not make any economic sense.
There is a false marketing commonly used. Many manufacturers claim their SMF battery can last 30,000 cycles. If that was true, most people would be able to install a normal SMF battery in a normal car and it should last almost the entire duration of the COE. 365 days x 10 years x 10 start stop cycles a day = 36,500 car engine starts. But most of the time, our lead acid batteries - regardless AGM, EFB or SMF - fail completely way before that.