It is a natural instinct among Ops staff to allocate adequate buffer when scheduling any event. At every juncture when the question arises whether to allocate more time to perform any task, we tend to opt for more time.
The thing is that such little buffers add up.
And it wouldn’t have mattered if there is no cost to such buffers. Many often dismiss such concerns with: “Better be safer than sorry.”
Probability
Nobody can deny that it is important to ensure there are buffers to deal with unforeseen events that may disrupt the schedule. Just as we often carry a little bit more cash in our wallets than we normally need, we should similarly provide corresponding time buffers when scheduling. While the likelihood of something unexpected happening is small (By definition, if it isn’t small, we would have expected them), we would be prudent to make the necessary allowance.
However, it is a good practice to take one step back at the end of each planning exercise to evaluate the sum of all buffers allocated.
When we look at a larger plan, we would undoubtedly find many pockets of buffers allocated. While the probability of any such event happening is low, the chance of all of them happening for the same project/event is miniscule, especially if there are many such events.
I think the mathematical term for this is compounded probablity. If the probability of an unlikely event happening is 1%, the probability that all 5 such events happening in the same project is 0.00000001%, or once every 10,000,000,000 (10 billion) projects.
So, when you have many such buffers, the chance that you will need to utlilise all the buffer times allocated is if every one of these events occur in the same project. And the chance of that happening is infinitesimal.
Assuming you were to buffer an additional day for each event, that would mean 5 days for each project. Imagine instead you buffer only 4 days each project instead of 5, i.e. save one day each project. You would then save 100 million days before encountering a project that will use up all the 4 days you have buffered.
Costs
When we think of the fallout from something bad happening, it is undoubtedly huge especially when compared against the cost of each time buffer. And that line of thinking results in us plumping (almost instinctively) for making more scheduling allowances whenever this question arises.
The thing is that while small, such costs are not insignificant, especially when we add them up.
Besides the Business cost of potentially losing new business when customers finds the longer time-to-market not suitable for their needs, we need also to consider the fact that extended timelines mean we have to juggle more items on our respective plates at any one time.
When we stretch out any timeline longer than necessary, we inevitably spend more time and attention on it, at the expense of other projects that we may be involved in. And with more projects on our minds, we become less able to focus our minds on doing each of them well.
This is akin to keeping excessive inventory. Just as inventory takes up physical storage space resulting in higher rental and storage costs, project checklists also soak up attention span and time in our mental space resulting in less space allocated to each project.
Final thoughts
Being conservative and prudent is indeed a valuable trait, and as professionals we should zealously ensure that adequate resources (time, manpower, etc) are allocated to get the job done well. At the same time, we also need to be just as disciplined to recognise the real costs involved so that we can strike an optimum balance based on rational and objective evaluations.