Expected life of copper H/W cylinder?

Does anybody know what is the average life of a domestic copper hot-water cylinder (tank) please? It's a 40-gallon exchanger type and a couple of pinhole leaks have appeared on the bottom seam. Am I on a hiding to nothing repairing them or can I expect the tank to last for a great deal longer? I'm in a fairly soft-water area.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
Add image file

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.