Enercell 1 5V Alkaline Batteries 2 Pack Review

I bought these Enercell batteries because they should last a long time and be of good quality. They arrived within five days and were in good condition. However, before I opened the box, I read the back - and the best before date was December 2015. It's been almost three years! The batteries work but I am concerned about how long they will last as they are past their sell by date. Also, they are as expected.