Question about ferrets lifespan

I have had two ferrets since 2016. On July 4, my ferret Pearl passed away suddenly and I think I’m going to lose her sister today. Her sister Wetzel has been struggling with insolinoma but Pearl seemed healthy except the night I put her to bed before she passed, I thought she seemed more tired than usual and she didn’t want much of her ferret vitamin.

Anyway they’re both 9, they are Marshall ferrets.

Is this a normal life span for them?

I feel like they lived good long lives yet I have read ferrets can live to 14 so I think they didn’t live long enough.

I’m very sad. I have two new ferrets I got for Wetzel when Pearl died. I pray they do better.