Usually flowers will start to wilt within 24 hours. Seeds take 3-6 weeks to ripen. You will know when the seed pods crack open. Earlier than that and you risk less than ripe seeds.
K

I'd expect it to take a month or more... the seed pods swell, then start to dry and crack open when the seeds are ready.... Don't pick the pod green...
I had great luck with Amaryllis Naked Lady this year, instead of seeds they produce like 2 or 4 little bulblets in a paper thin holder...and I planted them in and on moist soil and put a glass light fixture over them in semi shade and it looks like most of the 100 or so of them now have leaves !