Just this past weekend I replaced some Energizer Lithium Ultimate batteries that have been in my pins for 3 years.
For my WPC machines, they were about 1.6V
For my Whitestar machine, they were about 1.7V
Now these batteries measure around 1.8V when fresh, but if voltage has any relationship to "Leak potential", I could have easily got another 3 years out of them.