Per http://sharepoint.stackexchange.com/a/31205/9345,

It is the cache that is storing the previous version of the workbook in memory and therefore producing an out of date version. The best way to prevent this is to reduce the cache configuration against the Excel Services application to its lowest value. This would be recommended for a development Sharepoint instance so that you can see your changes immediately and then leave the production environments with a healthy cache duration to benefit performance to the end users.

Another thing you can do is update the XLViewer.aspx file in your Templates\Layouts Sharepoint installation directory. From here, you can add a small javascript block to immediately refresh the connections of the Excel Services viewer so that the view is refreshed on every visit. I'd only recommend this in your development environment though as it will negate the benefit of the server caching.

Here's an example of using the Excel Services client side API to refresh the connections:

    <script>
            var jQueryScriptOutputted = false;

            function initJQuery() {
                //if the jQuery object isn't available
                if (typeof(jQuery) == 'undefined') {
                    if (! jQueryScriptOutputted) 
                    {
                        jQueryScriptOutputted = true;
                        document.write("<scr" + "ipt type=\"text/javascript\" src=\"http://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js\"></scr" + "ipt>");
                    }
                    setTimeout("initJQuery()", 1000);
                } 
                else 
                {
                    $(document).ready(function() {
                        Ewa.EwaControl.add_applicationReady(SetupRefreshEwa);
                    });
                }
            }
            initJQuery();

            function SetupRefreshEwa()
            {
                om =Ewa.EwaControl.getInstances().getItem(0);
                om.getActiveWorkbook().refreshAllAsync(refreshAllAsyncCallBack); // automatically refresh all connections on open
            }
function refreshAllAsyncCallBack(asyncResult)
        {
            // Get the value from asyncResult if the asynchronous operation was successful.
            if (asyncResult.getCode() != 0)
            {
                 alert("Refresh operation failed with error message " + asyncResult.getDescription() + ".");
            }else{
                alert("Excel Analysis view refreshed on open");
            }
        } 
    </script>

Hope this answers your question.