If you don't plan to put many miles on your Box, then change it at least once a yr. If you plan to rack up some miles, then change it anywhere from 5K - 10K mi. The topic has been debated many times and there is no correct answer and you'll get passionate responses all over the board. It's how you feel that will be correct. There are many ideas why the IMS bearing fails on Boxsters, but one thought is the oil isn't changed often enough. Strictly theory but could have merit. I change the oil on my pair of 987s every 5-6K mi. If you do it yourself, it's worth it to do it more often than too little.
Welcome to the forum. Do a search on oil or IMS and you'll have at least a week's worth of reading. If you want to start a firestorm, ask which brand of oil to use or what brand of tire is the best.