From what I have seen from guys endurance racing Boxsters, the ONLY way to keep one alive for a long time without eating bearings is a dry sump system. With a dry sump, it should last a very, very long time. Tracks with long right handers are particularly tough on these cars. Look at
this thread. The data doesn't lie.
Getting a dry sump system together isn't cheap, but neither is losing multiple engines to oiling issues. You can try all the "bandaids" (deep sumps, X51 baffles, etc.) that don't work, or you can just go dry sump and not worry about oiling anymore.
P.S. Here is the
best thread if you want to learn about Boxster oiling. Chris knows his stuff.