hello - this will probably sound like an unpopular reply but I think realistically to finish within your time frame your phd does have to become the centre of your life. I have finished my phd now and did it on time as the thought of dragging it out longer was unbearable! I let it take over my life for one year and now I can spend the next however many I have left not worrying about it!
I think all things in moderation and I worked ridiculously hard and experienced burn out a few times but I had to curb the shopping trips and lays-in in the last year as I wanted to get it done. One day off a week worked really well for me and I found I had no guilt that I wasnt doing work during this time. Saying that, dont let your supervisor dictate to you how much you should work either - just tell him you work 24/ 7 on it to keep him schtum!

In my department people spend all/most of their time on the PhD. How else do you finish on time and get a life?

At least your supervisor show he cares and thats good !

starfruit, you shouldn't be working every minute of the day every day on the PhD just so you can look forward to getting a life, as you put it. Life has to carry on right through your PhD, or you'll be miserable! Trust me, I was there a couple of months ago, and my health was really starting to suffer. I went to a workshop on PhD life and what came out of it was that those who were getting a balance in their lives were having greater output on their projects than those who were completely obsessed by it. If you become obsessed, you tend to experience prolonged periods of inactivity from burn out, which means that you will probably end up having to take considerable time out anyway to get back on track.