Well...I was in grad school for five years, then dropped out after finishing all my coursework for my PhD but before writing my dissertation proposal. My husband got his PhD and now is a professor. I can't speak to your specific field (I was in the English dept, he's in Math) but I can maybe give you a few things that you might want to think about. Keep in mind that all of this is coming from someone who disliked grad school enough to drop out, so someone else might have a different perspective to offer.
First, you will probably want to make sure you have a realistic idea of what the job prospects are likely to be for your field. For the most part, academic jobs are very hard to come by, and there are people who spend years getting an advanced degree and then are unable to find a good job. As an example, my DH applied for jobs at about 150 different schools. From those applications, he got about 20 preliminary interviews and four on-campus interviews. He got four offers, and we considered ourselves very, very lucky to have that many places to choose from. Of those four offers, one was a postdoc for a very low salary, one was a postdoc for a decent salary but would only last two years, and one was a tenure-track offer in a place we didn't want to live. Quite a few of his classmates only had one job offer, so they had to take what they could get. These were people getting their PhDs from a top-ranked program. So--make sure you know what you're getting into before you invest time and money in getting a degree. Also, if you want to stop after your master's, make sure that you won't need a PhD to teach or work in a museum. In many fields, a master's isn't worth all that much and will at best get you a job teaching at a community college.
Second, there is usually a lot of relocation involved in getting a degree and then (if you're lucky) getting a good job. Most people move to wherever they got into school, then move again at least once to wherever their job is. This was part of the reason I dropped out--if I was lucky, I might get a good job, but it almost certainly wouldn't be in the same place as my husband's job. Then we both would have had to keep job-hopping until we could end up in the same place.
Third, going to grad school can be very taxing on one's emotions. When DH was applying for PhD programs, the brochure from Yale literally said, "Graduate school is a time of trauma and self-doubt." That isn't the case for everyone, but it was for me and DH. This was the biggest reason I dropped out of school. If you are more emotionally stable than I was at that point in my life, or if you choose not to go to a top-ranked program that involves a lot of pressure, your mileage may vary.
Basically, I think the key is to make sure that you understand all the negatives, then if you still want to do it, go for it.