I walked this path. Think about where you want to be when you're done. Are you married? Do you have kids? Do you want to do those things? If you want to be an academic, you have at least a decade of grueling work ahead. That's 4 years to do the Ph.D., and another 6 to get tenure, which is like doing three more dissertations worth of research while trying to manage a small group of young, inexperienced engineers. And that's if everything goes well. Precious little time for a spouse and kids. Ignore this ridiculous talk about learning to golf and taking vacations abroad. Nobody I know did that.
Personally, I finished the PhD in May and moved on to a really fantastic job in my field. I have time and money that I wouldn't have as an academic.
I'd like to clear up a few misconceptions I had about the academic lifestyle going in. This is about the professor job, not grad school.
1. Being a professor is not about teaching. I went into grad school thinking I could make a difference. Address the rampant gaps in my colleagues' education. It turns out that professors generally abhor teaching, and that departments actually use teaching assignments to punish underperforming faculty. Performance means papers and even more importantly grant money. Teaching doesn't enter into it.
2. Professors do not have any free time. Even tenured ones. That appealing academic calendar is a mirage. If you are a professor, you're a professor every waking minute. You spend your vacations at conferences, your summers trying to get ahead on research. You read papers before breakfast and after dinner. Or you burn out after getting tenure, get a heavy teaching load as punishment for your lack of productivity, and turn into the kind of professor everybody has an anecdote about. The one with nutjob politics who never turns up for office hours, or the one who lectures while hung over or still drunk.
Sorry to rant, grad school is no picnic and I wish I'd gone into it with my eyes wider open. I'm happy with the end result, personal growth, seeing things on a higher level, being "doctor" so-and-so, having an awesome job, but it's not at all an easy way out if you're tired of what you're doing now.