Ball Python Aging Signs

[Jolty]

I haven't really been able to find much information about this, but I am trying to figure out how old my friend's rescue ball python might be. He's had her for about five years now, and she was a rescue. He thinks she's elderly, but he's not sure because there was no information about her previous home.

Basically, the signs that make him think she might be older are:
- Really squishy sides. She's not obese or dehydrated, her skin is just very loose. It kind of reminds me of the way a human's skin loses elasticity as they age. However, she also has severe scarring from being burned all up her belly, so maybe the squishy, loose skin is from that.
- Can't climb very well. She can get around just fine on level surfaces and she periscopes quite a bit.
- Extremely good eater who readily accepts rats, mice, ASFs and quail with no issues. Despite eating 99% of her meals, she's still rather slender-looking.
- She doesn't feel muscular like other snakes. She just feels kind of like a long sandbag.
- Extremely docile, seems to tire easily, although it could just be her relaxed personality.

Are these signs of an advanced age? What other signs are there?