I second MRSMAC.
I had full plans of staying at work until 36-37 weeks,(I get really bored at home!!), but I only just made it to 34 weeks, due to fatigue and SPD.
Mind you I felt great right up until then, it just all hit me suddenly at 34 weeks.

Really in the end you need to do what is right for you.
Explain to DP that you know your body and abilities best, and that he needs to understand that. Failing that you could threaten to take up bunjy jumping! LOL

Good luck