I wish I could help, but all I can offer is a guess. 8-10 weeks? That's about how long I would give an amaryllis before I started watering again. I bet someone else could give better info.
I don't think the seeds need any cold treatment. I bet you have a decent amount of seeds, if you want to cover your bases plant one indoors, and plant another in a small pot and hide it somewhere in the fridge for a month or two before bringing it out to join the first.
I planted some last winter and left them outside in the cold. They germinated well come springtime..... third option? lol

I have lots of Galtonia in the garden, which I love, but have never tried forcing indoors. I have started lots from seed with no pretreating but don't remember how soon after harvesting. They are almost 100% viable, and I think you could start them anytime. Al