Warm up before you perform. Literally, a little practice before hand warms up your muscles and enables them to move quicker and more agile.
Practice your endurance. Time yourself to see how long you can maintain repetitive motions and practice to exceed your record. But while you're doing these exercises whatever you do STAY RELAXED. If you tense up and start gripping the stick too much your speed will gradually get slower over time not faster, as your technique deteriorates.
Record yourself playing. Many drummers are surprised at the quality of their playing, whether for better or for worse. When you listen to your recording you will be able to pick out rhythm/tempo inconsistencies and iron them out.
