I have read that colecting flowers just as the bloomfades is optimal unlike others like shasta daysys are suposed to dry compleatly on the plant.

Some plants suck the life out of the seeds back to the plant as they fade and thus become less sturdy.

I have noticed if you let marigold seeds sit on the plant they are softer and flatter also bends betwean your fingers so I asume picking them from your just faded blooms are optimal.