HI @Puneet Kohli 

Can you share the cohort definition? Are you setting the usertype property with an event or with an Identity API call?

I have created using the identity API

The cohort definition

is 

“where userType = premium”

”in the last 90 days” 

Note that it doesn’t matter what date range I use, the problem is the same

Since you are using the Identify API call to update this property, I suspect that not all of the 950 users have sent an event after this update. If an Identify call is sent after the event, the updated value is not reflected with the event. It will be reflected at the top of a user's profile, but will not appear in chart results until another event is sent after the Identify call.

So most likely only 176 of those could have sent an event which makes the property available and thus their inclusion in the cohort. I could be misinterpreting your case here, but let me know if you can verify this with some sample users. For a user not included in your cohort, check if their latest event has the userType property in the raw payload.

Is there no way to get them segmented into the cohort without waiting for them to send an event?

And for them to keep showing up in the cohort, do they need to have that property within the last N days on their events, or once I set the property on the user it stays there even if I don’t send that value for future events?

Here’s a detailed understanding on how Amplitude applies user properties.

Once a user property is set on a user, it will persist on all future events unless you change it’s value explicitly.