I haven’t really chosen to curse anyone in some time now, but nonetheless, I used to be pretty obsessed with it when younger and angrier. In any case, I think I can grasp your concerns about the time frame aspect given your likely emotional attachment to the situation if nothing else. Most important as you can possibly guess is to never doubt the coming manifestation; assume it’s a success always. Unless eventually doubting was what you’d needed to finally let go: it isn’t that black and white. Cursing is the easiest form of magick either way. It’s true that everything naturally falls apart without our help. Therefore, even a neophyte with enough hate and a basic psychic connection could do a good bit of damage to the average person.
I would say to have the highest chance of a speedy success in any case you’ll want to work the rite until you have almost made peace with your target; until you kind of almost feel moved on, or more literally like you’ve exhausted most of your rage or whatever you’d been feeling. With this, let your attachment to it all go, and passively expect a result thereafter without worrying. I think EA mentioned this concept as being the law of inverse effort or similar. Alongside the need for certainty of success, those are both incredibly important concepts and details for sorcery, and regarding time-frames: no less. Ignoring this advice will extend the time until manifestation perhaps indefinitely.
I’ve had overnight results in hours with things like triggering a bad, lingering cold with one ex that’d broken up with me on a trip after calling on Belial. Yet, that was just enchanting for a small and general ill will type of outcome I hadn’t specified; it arguably and probably didn’t require as much rearranging of reality, as say, with carrying out a death wish scenario. Having been on both sides of that coin, and also having instructed another successfully more than once, I’m sure by now it may still vary from case to case quite significantly for untold and unseen reasons. (Link: Phil Hine: “Analytic Techniques for Sorcery Interventions”). But it’s easy to assume a period of a few days to two weeks or so could be reasonable in many smaller cases. Then again with death curses you might possibly see a time period of months – maybe even years – and more commonly deaths happening from cancer or another sudden illness if you meant you’re going to that extreme. That said: if you’re trying to curse someone to extremes without sheer sadism, a seemingly unquenchable hatred, or both, then it’s probably not going to happen. Curses often work so well, I think, because we want them to work so badly: almost can need them to work so badly. Similarly then one must consider how much your heart is in whatever you’ve been working toward before answering your own question about any potential time frame, perhaps.
Otherwise, are you working with a spirit for this curse rite? If so, they may be able to give you advice or help by pointing you in the direction of another spirit; from providing us with sudden intuitions to literal advice. Setting a specific time frame with said spirit may even on some level help you view your goal more objectively; making it easier for you indirectly thereby, as well.
Again, keep in mind that the time frames above aren’t going to necessarily hold true, of course. Really, who knows how long it will or should take in any one case? I’m just being fair – yours was a good question we’ve all asked ourselves. Maybe the seemingly commonplace thinking that the result being bigger therefore means it should take longer to manifest is actually just like assuming that more costly products are automatically better merely because the cost alone is bigger; an erroneous correlation: a limiting belief we may impose upon ourselves. In any case though, it isn’t hard to imagine that the more specific you will choose to get with your curses, then the easier it becomes to assume a longer time for the goal to manifest.
Good luck in any case.