Promotional entitlement with custom expiration not extending correctly on renewal

Hi,

I’m implementing team subscriptions where an admin has a normal auto-renewing subscription, and team members receive a promotional entitlement that expires at the same time as the admin’s current period.

On renewal, I try to extend the members’ entitlement by calling the V1 “grant promotional entitlement” endpoint again with a new end_time_ms.
 

const url = `https://api.revenuecat.com/v1/subscribers/${encodeURIComponent(appUserId)}/entitlements/${encodeURIComponent(entitlementId)}/promotional`;
const response = await fetch(
  url,
  {
    method: 'POST',
    headers: {
      Authorization: `Bearer ${revenueCatApiKey.value()}`,
      'Content-Type': 'application/json',
    },
    body: JSON.stringify(
      {
        end_time_ms: endsAtMs,
      }
    ),
  }
);

Response:

{
  insertId: "699397e5000ee469665d0539"
  jsonPayload: {
    appUserId: "okolifiqPsTzY10TRV9yA627o3w2"
    endsAtMs: 1771281961210
    entitlementId: "Team Pro Access"
    expiresAt: "2026-02-16T22:46:01.210Z"
    message: "rc:grant_entitlement_success"
    responseBody: {
      request_date: "2026-02-16T22:19:17Z"
      request_date_ms: 1771280357932
      subscriber: {
        entitlements: {
          Team Pro Access: {
            expires_date: "2026-02-16T21:46:01Z"
            product_identifier: "rc_promo_Team Pro Access_custom"
            purchase_date: "2026-02-16T21:19:05Z"
          }
        }
        first_seen: "2026-02-12T20:10:28Z"
        last_seen: "2026-02-13T20:12:45Z"
        non_subscriptions: {
          0
        }
        original_app_user_id: "okolifiqPsTzY10TRV9yA627o3w2"
        other_purchases: {
          0
        }
        subscriptions: {
          rc_promo_Team Pro Access_custom: {
            expires_date: "2026-02-16T21:46:01Z"
            is_sandbox: false
            original_purchase_date: "2026-02-16T21:19:05Z"
            period_type: "normal"
            price: {
              2
            }
            purchase_date: "2026-02-16T21:19:05Z"
            store: "promotional"
            store_transaction_id: "1bbdbf1ab911a470fca79c2876ad6d64"
          }
        }
      }
      status: 201
    }

• The API returns 201.

• However, the entitlement expiration sometimes remains at the previous value.

• After the old expiration passes, the member loses access.

• This seems more frequent when the new expiration is close to the current one (tested only sandbox).

Questions:

1. Is it officially supported to “extend” an already active promotional entitlement by calling the grant endpoint again with a later end_time_ms?

2. Are there timing limitations when the new expiration is close to the existing expiration?

3. Is the recommended approach for team subscriptions instead to grant lifetime promo entitlements and only revoke on admin subscription loss?

I want to confirm whether syncing member entitlements to each renewal via end_time_ms is a supported production-safe pattern, or if this is expected behavior.

Thanks.