How long does battery last on a 7th generation iPod Nano?

Hi guys. In March 2019, I bought a brand new 7th generation iPod Nano and I unboxed it in February this year. I didn't unbox it at the time because I was abroad for almost a year and came back 2 months ago (in February).

On the one hand, I've noticed the battery life isn't as long as Apple states it is on their website. On the other hand, according to the specifications on the Apple website, battery life for this device is up to 30 hours of music and 3 hours of video.

Now, because I don't have any songs to play on my iPod, I use it to listen to the FM Radio. However, the device's battery life only lasts 7 hours and a half if I continuously listen to the FM Radio.

In fact, yesterday I tested it to see how long the battery would last. So I left it in my bed playing the FM Radio by itself. It started playing at 3:48 pm until it completely drained exactly at 11:12 pm.

I don't know why I'm not getting ''the 30 hr play time'' if I rarely use the screen and have bluetooth off.

To be honest, I've restored it to factory settings twice without it making any difference in battery life.

Another thing I'd like to mention is that it heats up a bit while charging. I charge it via my laptop with no wall charger.

Is that normal?

Do you think the battery needs replacing?

For those who own this iPod model: How long does your iPod's battery last?

Does it last up to 30 hours like Apple advertises?

Sorry for asking too many questions. As you can see, this is my first Apple product I ever own.

Thanks in advance and sorry for my english. It's not my native language, though.