- Funding: Even if you were one of the lucky ones, your funding will probably run out after the 3rd year. Now, a few chapters still to go, you really need the money.

- Time: the end of the 3rd years seemed so far away...

- Supervisor: the laid back, super cool supervisor you used to have turns into an evil academic monster.

- Family: they never understood what you did. Still a student?, they thought. You are supposed to be finishing, things slow down, but you find yourself telling your mum on the phone: I'm looking for a part-time job, in a library or something... And now they really think you have a Peter Pan complex.

- Girfriend/boyfriend: She or he has a proper job, earns a salary and pays for your take aways. You used to buy her or him ice creams and the occassional £25 dinner. Now she or him becomes more like your mum or dad. You find yourself constantly borrowing £5 from her/him. Her or his friends, of course, are all graphic designers or something, and go to places where a beer is £5.

- And, finally, the thesis: it is shite.

Ahh, I sympathise, except my supervisor is an evil monster disguised as someone nice.
The parent comments They've stepped up now I've submitted....

I meant my supervisor was like that from the start....

I think any year past the first three start to make you feel desparate or "This is never going to end". The funding running out can make you focussed or it can make you panic and bury your head in the sand.

I think the big "What happens next" is a fourth year question that disturbs a lot of people, as is "Is my research going to be out of date before it has even been published?"