Formula or Pivot? Advice welcomed on how to achieve customer lifetime statistics

Hi All,

I have a spreadsheet with approx 15,000 individual invoice transactions, each row with a date, value and customer name.

Using a pivot, I can easily work out a total lifetime value of each unique customer along with how many transactions that customer placed, but what I cannot figure out is how to calculate how long that customer has been with us?

I am hoping, given that each transaction has a date, that I can somehow work out the length of time between the earliest date a customer has ordered, to the last date a customer has ordered.

I just have no idea how!

I attach a very small sample of the data here and would be most appreciative for advice.
Many thanks