There are a couple different factors. We have an explainer, but the gist is that
conversions are the important metric. We recommend having at least 100-200 conversions per variation. If your conversion rate (whatever you're testing for) hits that target, then you can likely test with statsig results, within a reasonable amount of time.
https://docs.growthbook.io/faq#how-much-traffic-do-i-need-to-run-ab-tests
Also, we recently released a power calculator, under the Experiments page. It allows you to figure out if/when you'll reach statsig.
https://docs.growthbook.io/statistics/power