Buffers are not padding
A buffer with a named job survives the week; a percentage does not.
Padding is silent, buffers are named
Adding twenty per cent to every estimate and calling it a buffer is padding. Nobody knows what it is for, so it gets consumed by the first small delay and then the plan is late anyway. A buffer with a purpose is spent only when that purpose happens.
Three buffers are enough
Review, client lag and rework cover most project delay. Review protects quality, client lag protects the calendar from a slow approval, and rework is funded by the revision cap rather than by goodwill.
Give each buffer a trigger
The review buffer starts when the draft is sent. The client lag buffer starts when a decision is requested. The rework buffer starts when a round is used. Without a trigger, a buffer becomes general slack and disappears.
Unused buffers are evidence
A buffer that survived the project is not wasted time; it is proof that the estimate can be tightened next time. Record it and adjust, rather than quietly absorbing it into the next quote.