Basically, it's up to you.
There are good reasons to alter bevel depth, depending on external circumstances such as design load, access, distortion, weld process, etc...
Questions are:
Are you working to a particular code or standard?
Does the joint require complete weld penetration?
Do you intend to back gouge?
What type of material?
Some codes have pre-qualified procedures that specify joint dimensions.
Most have a process detailed for qualifying reliable procedures based on proposed joint conditions.
Tim