What is the average life expectancy of a male dachshund?

My weenie dog is getting older, he was red but is now mostly white LOL and I am so attached. He is 13 years old and except for some minor aches and pains on cold days his only problem is that he now eats mostly softer food such as those gaines burgers type. I dearly love him and just want an idea of how many years he might have left and perhaps some ways to make those easier for him. Thanks.