Beeminder kind of barely works for things that are that short term (any less than a week and it definitely doesn’t work). Have you checked out our TaskRatchet integration? That’s focused on one-off tasks.
(Also I hate to suggest it but it’s possible StickK might work better for short-term things like that. Please report back if you try StickK! I haven’t tried it in a long time. It was pretty abysmal compared to Beeminder last time I did and I’d love to know if they’ve improved in the meantime.)
I think this is correct. I’ve been thinking for a while that we, ironically, need more friction in the goal creation process. Including your suggestion: you should be asked explicitly when creating a goal when, if ever, it should end. I don’t think the status quo is too bad, where the goal is created and you can then adjust things like the end date, but having that be part of goal creation would be better.