Question

How long do the seeds remain alive after they are dispersed?

Answer 1

Viability means the condition of being alive and in case of seeds it means the ability to germinate.
Seeds viability differs from species to species, some seeds lose their viability in a day or two. Example: Zizania aquatica loses viability within days if exposed to air.
Some seeds retain viability for several years. Example: Lupinus arcticus.