Opening and closing time are usually estimated or calculated for several purposes:
a) To avoid water hammer (liquid pressure peaks) that will damage equipment. The pressure peaks might under wrong circumstances (too abrupt closing) be well over allowed pressure limits for the equipment. Searching general on net and/or all forums here for keywoords 'water hammer' you will find several references to calculations and estimating methods.
b) To be well within suitable figures for the mechanical equipment (electrical, pneumatical or other orbiturators normal operating standards). Figueres after manufacturors recommandation, process consideration and for regulating valves to give well damped opearations. To high frequency regulations and abrupt movements to be avoided. 'As long as possible' or normal for equipment often sought rather than fastest.
c) To satisfy emergency shutdown valves need to shut down fast. Often for larger valves and water regulated in two steps: for instance 70-80% fast, rest slower to avoid water hammer. Mechanical: producers linits. Pipeline calculations as point a.