A little seed goes a long way.

[Cavoodle]

A country friend of my wife brought down some seed on her trip to the easter show - Bambatsi, Single Digit and Gatton. I thought I was onto a good thing but only got a small ziplock bag and the advice that the seed’s treated so don’t feed to the birds and that this is enough to sow an acre of land.Only need another 3,200 square metres after I knock down the house and I won’t need to waste the seed.

[Buzzard-1]

Still worth planting some for seed heads and nesting material

[Diane]

You might never have to buy seed again.

[monotwine]

IF your seed heads / seeds are kept dry in a fairly stable environment (humidity and temperature) they should be viable for many years to come. Most grasses are pioneers and can go for extented periods in dormancy until the right time. Don't know for sure about those particular types, but your little bits may keep your birds happy for a long long time.