REMIND HER A DISSERTATION IS A SMALL FIRST WORK, NOT A MAGNUM OPUS.
A PhD degree is designed to introduce you to the company of scholars and ensure that you will have something to say in the future. The dissertation then, is one work, not the ultimate effort. Encourage your spouse to think of it as an important but not all-consuming step in their scholarly development. In other words, gently remind them to get it done and stop being a perfectionist for once.
RELIEVE HIM OF WORK AND FINANCIAL BURDENS IF POSSIBLE.
You may not have the financial resources or employment opportunities to do this. But if you can, it will rapidly speed up the dissertation process. You may even want to have an honest discussion about debt as an investment. If not working this year causes 10,000 of student loans to accrue that might scare you. But recognize that for most people leaving a PhD program with a degree in hand they will get a 15,000 raise simply by working full time with benefits in an established institution. So, you may be costing yourself money by refusing to take on debt. Sometimes simply being relieved of the commitment to 'no debt' can empty a PhD student's schedule and focus their study.
DECIDE ON A TARGET MOVING DATE FOR THE END OF THE PHD EXPERIENCE.
It is totally fine for you to say to your spouse 'We can stay here for four years, then you have to finish what's left somewhere else.' This may or may not apply if your partner is pursuing an online PhD. However, you do have a career and a life after all. Don't be the sacrificial spouse that completely sidelines his or her life for ten years while a spouse takes their sweet time pursuing their dreams. A deadline does wonders for many people. Set a date, and start the countdown. You will feel better, and your spouse may write faster!
SET UP A SYSTEM OF GOALS AND REWARDS FOR HER PHD ADVANCEMENT.
Have a conversation with your spouse about how they would like to celebrate certain milestones. Come up with ideas and write them down on paper! If your spouse knows a weekend away with you is coming as soon as that dissertation proposal is accepted it may be just enough motivation. If she knows you are heading to Florida for a week once chapter two is done you may see the fingers fly on the dissertation keyboard. Try mentioning "Caribbean" or "Italy" or "a new Mac" for a celebration of the completed dissertation. This way you aren't nagging or hassling your spouse about the PhD, just providing motivation to get it done!
BE HONEST ABOUT YOUR DREAMS AND LIFE GOALS.
Many spouses are fully supportive and mutually sacrificial if goals are simply clearly stated. Let it be known that you want another child, want another degree, or want to get back closer to family sooner than later. You don't want to guilt your spouse for getting the PhD program, but you want to be honest about your dreams for life. And they probably don't involve staying in school forever (that might be your spouse's fantasy!)
HOLD YOUR PHD SPOUSE TO COMMITMENTS TO FINISH.
If your spouse committed to a move date, stick to it. Unless there are some really strong reasons for staying that cannot be attributed to your spouse's lack of diligence rent the truck and start packing! Of course you should be flexible if some unexpected tragedy occurs, a major disappointment happens (someone wrote it first!), or other situations out of their control force a change.
LISTEN TO YOUR SPOUSE TALK ABOUT THE DISSERTATION AND TRY TO UNDERSTAND.
I know, I know, I know. This is like poking out your eyes or pulling off your finger nails. Think of it this way, your spouse probably doesn't have many people other than an advisory (who isn't always safe) to talk to about the ideas spinning in the head. Even if you DON'T understand what the heck 'transversal logic in social sciences' means, you can provide an ear that is safe. If you do, often they will have key insights into their dissertation simply by hearing themselves talk about it out loud. In other words, but not shutting them up, you might shave off a month. Let them talk about it every other day or so, and you might shave off a year of the PhD program and dissertation writing process.