Have you encountered the calculation of the deadline, taking into account the improvements?

Question

Preparation of terms of reference

Hello.
Have you encountered the fact that in development tasks, the task director requests a deadline for the task, taking into account possible improvements?
It turns out something like this algorithm:

1. There is a basic understanding of the task (without discussing the details) and the task is set
   
2. The task is completed and a list of improvements (changes) is received from the director
   
3. The performer finalizes and, if there are no new improvements, then the task is considered completed
   

The task manager requests deadlines for tasks taking into account the entire process, i.e. By the specified deadline, the task must be completed, taking into account all the improvements that are not known before the start of the task (respectively, when assigning a deadline).
There are two additional moment - deadlines cannot be "cosmic", i.e. with a significant margin and the task manager is constantly in operational communication for a prompt response.
Have you come across a similar scheme? What are the opinions on this issue?

Answer 1

In fact, revision is a separate task that must go through the same stages as the previous task. Therefore, it is simply impossible to do such a recursive evaluation.
Evaluating tasks, the essence of which is unknown, is simply meaningless. There is only one possibility to name an adequate term in this case - to guess by chance.
When evaluating labor costs according to detailed technical specifications, errors occur every now and then, let alone spherical improvements in a vacuum.
If someone offered me such a scheme of work, I would try to explain its failure. If the explanations lead nowhere, I will refuse to work, regardless of the temptation of the task or the payment - the risks are too great, and in the end it is always the performer who is to blame.

Answer 2

There are two types of improvements:
1) from a misunderstood TOR
2) from changed customer requirements,
they usually add 30% of the time, calling it an estimate, i.e. an estimated outfit, and not 100% accurate, but with improvements like (a) you need to deal with it at the beginning of work or even before