A common problem with Google Earth is long loading times due to having a lot of stuff in your ‘My Places’. Google Earth stores your ‘My Places’ in a KML file appropriately called myplaces.kml. Exactly where that file is stored depends on your operating system. See this page if you need to know where to find it. The myplaces.kml file is loaded when you open Google Earth and only saved when you exit, or if you explicitly save it during the session.
If you notice Google Earth is taking longer to load than it used to, then the most likely cause is a large myplaces.kml file. Before proceeding with the following tip, it is highly recommended that you backup your ‘My Places’. Simply right-click on the topmost folder and select ‘Save Place As’ then select where you want to back it up to.
The first step is to go through your saved places and remove anything you no-longer need. However, if you still have a number of items that you wish to keep and loading is still slow, then one trick is to move items out of your myplaces.kml file and into separate files that are referenced via a special feature called a network link. You probably don’t need to worry about placemarks that you have personally created as they typically take up very little space in KML. The real culprits are KML files you have imported from elsewhere that have a large number of items. For example, we found that just one item, a map of world borders constituted nearly a quarter of our myplaces.kml files size. The downside of moving items to network linked files is that you can no-longer edit them directly, so look for items that you don’t intend to edit in future.
Once you have identified an item you wish to extract, right-click on it and select ‘Save Place As’. Select a place to save it to on your computer that will remain accessible and that you won’t delete by mistake. Now right-click on ‘My Places’ and select Add->Network Link. Give your network link a useful name and click ‘browse’ and select the file you saved earlier. You should now see the items you saved in the new network link folder and you can safely delete the old version of it from My Places. Repeat this for other items, or alternatively put all the items you wish to extract into a single folder and do the above procedure only once.
Using the above tactic we were able to bring our ‘myplaces.kml’ file down from 40Mb to just 5Mb and Google Earth is loading a lot faster.
Keep the network links deselected and Google Earth will not bother reading when loading.