depends on the task itself. Some of them - once in a few days. But there are monthly tasks that are only checked once the month ends. Like there's one for telegram chat superstar - that's only 1 person, that's performed better than the rest during the month. So once the month is over - the 'hero' is chosen.
because the nature of telegram chat superstar is more like contest that won by 1 person is understandable they checked it once a month.
i'm more curious with task that give reward to everyone like reddit task and youtube task, how long they gonna process the reward?
all of my task from 2 days ago are now in "complete" status, looks like the checking process take 2 days.