How long before you need them should you ask for letters of recommendation for academic jobs? I've heard the etiquette is to ask 3-4 months in advance, but haven't found much corroboration for that. Honestly, that seems like quite a long time. Would asking as late as 6 weeks in advance come across as rude?
I can't speak for everyone, but 6 weeks would be fine for me personally. Less than 2 weeks I'd be grumpy about, if there weren't a good reason.