Add advice about saving the colab

notebooks/unit3/unit3.ipynb

@@ -134,6 +134,22 @@
         "For more information about the certification process, check this section 👉 https://huggingface.co/deep-rl-course/en/unit0/introduction#certification-process"
       ]
     },
+    {
+      "cell_type": "markdown",
+      "source": [
+        "## An advice 💡\n",
+        "It's better to run this colab in a copy on your Google Drive, so that **if it timeouts** you still have the saved notebook on your Google Drive and do not need to fill everything from scratch.\n",
+        "\n",
+        "To do that you can either do `Ctrl + S` or `File > Save a copy in Google Drive.`\n",
+        "\n",
+        "Also, we're going to **train it for 90 minutes with 1M timesteps**. By typing `!nvidia-smi` will tell you what GPU you're using.\n",
+        "\n",
+        "And if you want to train more such 10 million steps, this will take about 9 hours, potentially resulting in Colab timing out. In that case, I recommend running this on your local computer (or somewhere else). Just click on: `File>Download`. "
+      ],
+      "metadata": {
+        "id": "Nc8BnyVEc3Ys"
+      }
+    },
     {
       "cell_type": "markdown",
       "source": [