It's perfectly natural for a force user to die from falling down a long pit or being stabbed with a lightsaber!
Lesse, a lot of the NJO ones likely do live out til the end. There doesn't seem to be any big threats after Abeloth, until the Lost Tribe comes up.
One issue is life extension means they sometimes do just last until something *can* finally take them down. T'ra Saa, Ood Bnar, Ikrit, Andeddu, Celeste Morne, Krayt, Vitiate.... so many multi-century lifespan people still find a death.
Oh, K'Kruhk seems like he made it to old age, and it's hard to imagine something coming along and putting him down before his final call.