How long do these lasts for?

As per the title.

I recently purchased a lion head as a gift for my family member. It's going to be used as a display for his home. Currently he's storing it in a dry place away from the sun and it's inside a clear plastic pvc garbage bag (heavy duty ones).

Since it 's paper mache i'm kind of worried that paint and mache will decompose over time.

Was wondering if you guys know how to preserve it e.t.c.