Is it normal for iPhone 15 Pro Max battery life to be at 99% after 6 months?

No, it's actually better that normal.

Batteries degrade over time with usage due to chemical aging, that's just how they work.

You can expect about a 1% drop per month with average use on an iPhone. This is an approximation, that is why it may be plus or minus a few percent on a month to month basis.

Apple recommends replacing it when it reaches 80%. To check your battery health, go to Settings > Battery > Battery Health.

iPhone Battery Replacement.

iPhone Battery Service - Apple Support

About Lithium Ion Batteries

iPhone battery and performance - Apple Support (IN)

Here are some tips on maximizing battery life.

Batteries - Maximizing Performance - Apple

This is normal. My iphone 15 pro max has 63 charge cycles and has 99% battery health.

I’ve had mine since October 2023, my battery health is now 90% with cycle count of 280. I’ve never experienced my battery health going down this quick ever and I’m confused how this works. I do think my battery doesn’t last as long as it should