Three for each drone, cycled religiously (OCD) 😁
Recently retired batt #1&2 for both Mavic 2's after 6 years of use - road-testing the decent quality 3rd party non-OEM replacements... so far: so good.
Then you'll get to pay $10000 in advance for an obstacle avoidance feature that's "coming soon", wait 10 years without it ever appearing, and be told that it'll actually need new hardware and not be anywhere as capable as what was advertised when...