Simply split the capsule in two and add to 100ml of deionised/distilled water and mix.
No minimum shelf life.
These buffer solution capsules for use with pH electrodes are convenient and easy to use.

Chemistry School Lab Equipment Suppliers in India 

Ltekonline are the manufacturers of Buffer Solution Capsules PH Meter used to demonstrate engineering principles in Engineering Colleges, Engineering Schools and Chemistry Lab Equipment for Engineering Teaching Lab in Universities