is it normal if battery health drops to 99 in 5 months

Wow. That's amazing. Battery Health normally drops on average at about 1% a month, so after 5 months, you would expect the battery reading to be in the 94-96 range.

You might want to send flowers to Apple for your good luck.

But, averages are averages over time. Some months, the battery will not decline at all, then it might drop 2-3% the next month.

So, after 12 months, your battery will likely be in the 88-90% range. This is normal and expected. My phone is 12 months old. The battery is at 89%.

If you can get 2 years out of the battery, you will be doing very well.

I can only speak for myself and the 3 iPhones here. My answer is based on 15 years experience on these support boards.

If other users comment to this thread, I think you will see the 1% loss on average per month confirmed, so you might want to make an appointment at the Apple Store or take the phone to an authorized Apple service shop.

They are going to tell you the same thing, but at least you will have other opinions.

I would be thrilled if my battery performance was anywhere near as good as yours. Good luck.

Only a 1% drop in 5 months? That's simply amazing and fantastic! As Bob said above, on average, you can see about 1% loss in Battery Health per month, so it would honestly be normal, if your phones Battery Health was 95% at this point. Keep doing what you're doing as your battery is great.