Let's say that I'm working in a team of QA Testers. And some automation responsibility comes along. So my boss assigns it to me. This isn't a one time task. This is more like a work-every-week for the rest of my career over here or at least until the automation tool goes obsolete.
Then some other tool + extra automation work is required from the higher management. That gets assigned to me too. Also a responsibility rather than a task.
Next, the higher management makes a couple of demands about things that we should be doing. One of them goes to my colleague and the rest two come onto my plate.
And this process goes on and on.
Whenever I tell my boss that I'm loaded with tasks right now and cannot take anymore, he asks me to define the tasks. There's a blocker for responsibility A, and there's a little bit of waiting time for responsibility B. Using this my boss says that I do have some time to squeeze by to take up an additional responsibility and that it's all doable. Discussions about how much time each tasks take don't lead anywhere because the boss has his own notions of how some ex-employee in the past was able to do it all.
I hope that the scenario that I'm defining above brings out the proper context in which I"m asking this question.
Is there a way to define how much responsibility can be assigned to a person? Or are there no limits because "the employee must have a can-do attitude" and "everything can be done if you will it"?