Do grobags lose their warmth eventually?

[Pico2]

DD's grobags have been through at least 3 other children, so have been used for 3 years already. This morning I noticed that her feet were cold in her grobag. Obviously I'm used to her having cold hands in the morning, but I would have thought that her feet would be warm. I'm trying to decide whether to get a new grobag or if she is a naturally cold footed baby.

[FATEdestiny]

I'm not sure how you would be a to tell factually, rather than anecdotally?

I have grobags and various sleeping bags that are currently being used by my fourth child. Some are now over 10 years old.

The older ones do feel thinner than newer ones. But then all of my children have had different temperature preferences, so have worn different clothes to sleep in.

While one of my children would wear just a l/s vest and 2.5 bag in winter and was always too hot, another was mostly cold and wore vest plus sleepsuit in winter. That was just their preference.