'Old' in the Bible

Meanwhile, Saul's son Jonathan had a son whose feet were crippled. When he was five years old, news had arrived about Saul and Jonathan from Jezreel, and his nurse picked him up to flee, but in her hurry to leave, he happened to fall and became lame. His name was Mephibosheth.

David began to reign when he was 30 years old, and he reigned 40 years.

Now Barzillai was a very old man at the age of 80 years. A very wealthy man, Barzillai had provided for king David during his sojourn in Mahanaim.

I'm now 80 years old! I can hardly tell the difference between what tastes good or bad! I can't tell what I eat or drink! I can't hear the voice of men and women when they sing! So why should your servant be an added burden to your majesty the king?