I think that a PhD is valuable in that if you want to get into a good debate about a real issue and not just go back over things that should already be understood, then you need to be able to get into the ring with people who have been seeking the same goal. There’s a ton of self taught philosophers who come to some good conclusions and can be indistinguishable from academic philosophers. However, I’d say that at least half of the things that I read or talk to self taught philosohers about aren’t even real arguments, just attempts to understand real arguments. If you get an undergrad degree in philosophy, then get a PhD, you’ve probably been studying for about 10 years. I doubt there is a large percentage if people on ILP with ten years of intensive philosophical study under thier belts. I have alot of fun on this forum and there’s plenty of good information here, but most of the things that I can think of to post are more a product of my sense of humor than of my strategy of philosophical inquiry. If all you want to do is learn philosophy and use it to enrich you life, then there’s no need to go to school. If you want to come out ten years from now and publish serious philosophical essays addressing the current problems of the dicipline and helping the evolution of it, then you’ll have to have a PhD, or a miracle.
Just a heads-up, but even with a PhD, it’s hard to get into the field. I’ve just finished my master’s and haven’t been able tog et anything but some low-paying adjunct jobs. But I’ve known people with PhDs from universities big in their field have to wait 20 years before getting tenure. Unfortunately, the field is relatively small and the professors never leave. One has better luck in getting a degree in a related field (my advisor who has his PhD from Harvard in philosophy teaches religious theory) as it’s likely to be easier to breach into.
You don’t have to teach necessarily. You could get a degree and then be more equipped to pursue more philosophy on your own time, while taking a think tank job somewhere to pay the bills.