Depends on the chickens perhaps? One of my chickens definitely goes broody within a week or max 10 days, if I leave a clutch of eggs in the nest. But only in spring and early summer.
If I don’t leave eggs in the nestboxes they don't go broody that much.
There are hens that go broody often and hens that rarely get broody. Even my bantam RIR got broody early summer last year. This year I had my first broody about 5-6 days ago. With real spring weather.
Last year I bought chalk and rubber eggs from the toy shop. They only sell them in the period...