Our pricing structure, with the credits/expirations/cooldown/restrictions etc. is admittedly a little weird and inconvenient, but it is that way in order to ensure that we can keep the minimum price required to receive official feedback low, while also ensuring that we can pay our teaching assistants fairly for their work. We achieve this through the fact that this system allows those students with tighter budgets to pledge when they need credits and cancel in the interim, while also allowing those with more flexible budgets to maintain continuous pledges and risk (or voluntarily allow) their credits expiring.

Those expired credits go towards subsidizing the overall cost of the feedback (for which we pay our teaching assistants roughly twice what the students pay to receive it), and the other restrictions - such as the 2 week cooldown - works towards increasing the chances that the work being submitted is not rushed in any way, which tends to increase the amount of work involved in a given critique. It is of course absolutely possible that a student might complete Lesson 3 in 7 days while adhering to all the requirements of investing as much time as they require to do the work to the best of their current ability, but by maintaining a hard cooldown of 14 days, we greatly reduce the added labour that would be necessary, ultimately allowing us to leverage our very limited resources more effectively.

Of course, this means that allowing students to bypass these restrictions would seriously compromise our ability to function and provide this service. That said, I would recommend that if you are in a position where you must avoid having credits expire, it's best that you not maintain a continuous pledge, but rather sign up when you need credits, and cancel in between.