Sure, I quite agree with that in general but I usually prefer to set up a schedule and that's mostly for me. I work better like that otherwise it's an open route to lazyness.
The dates I give are always estimates with enough margin to not be worried about being too far behind schedule, and if one or two more weeks are needed, I take them and I don't think anyone will realize nor mind it too much as long as it is reasonable.
Thankfully the code of my games is not complicated enough to have bugs that take months to solve. At worst, it takes 1 hour to solve. But yeah shit can happen like having the hardware crash or get corrupted resulting in the loss of all my files... (But I made some copies in different places so even that should not be a big drawback).
If one day I come up with the excuse that I have an unsolvable bug in the RenPy code, I think you can safely call it bullshit