I'm running Mavericks, 10.9.5, on my late '09 27" iMac 11,1 2.8 GHz Intel Quad Core i7 16 GB 1067 MHz DDR3. It is running fine except for an occasional fail to wake from sleep overnight. I'm concerned that if I get too far behind OS releases I won't be able to update in the future. What about application compatibilty? I am running OS from an external SSD and have a second SSD that I can install 10.2 on. What is the best way to migrate my apps and files to the new OS?