hello bro, with headphones other than airpods or airpods pro, we have to manually go to bluetooth settings and pair the headphone. If its airpods apple have implemented hand off feature, but with multiple device nearby we can use control center to connect the airpods quickly by pressing the bluetooth icon and selecting airpods.
But with apple watch it automatically connects mostly when you have paired it with iPhone. airpods is chosen by people mainly for its convenience.
airpods lifetime is 2.5 years to 3 years average.
getting applecare+ for airpods when we buy and if we damaged it by end of 2 years before warranty ends then we can get new airpods or airpods pro by paying service fee of 2500 to get new ones. that will give 2.5 years to 3 years average battery life.
if you dont want to spend much on airpods, you may manually try pairing sony headphone with your mac and iphone.