diff --git a/.github/workflows/ubuntu-cuda.yml b/.github/workflows/ubuntu-cuda.yml
index 9691ab0ed30..ce4528a83ca 100644
--- a/.github/workflows/ubuntu-cuda.yml
+++ b/.github/workflows/ubuntu-cuda.yml
@@ -11,7 +11,8 @@ on:
     branches:
       - main
   pull_request:
-    types: [opened, reopened, synchronize]
+    # Reduce CI frequency for paid CI.
+    types: [review_requested]
 
 concurrency:
   group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
diff --git a/.github/workflows/ubuntu-openblas.yml b/.github/workflows/ubuntu-openblas.yml
index eb11202a3ab..233c32bd96f 100644
--- a/.github/workflows/ubuntu-openblas.yml
+++ b/.github/workflows/ubuntu-openblas.yml
@@ -6,7 +6,8 @@ on:
     branches:
       - main
   pull_request:
-    types: [opened, reopened, synchronize]
+    # Reduce CI frequency for paid CI.
+    types: [review_requested]
 
 concurrency:
   group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}