I use Paxil to help with my PE, which is a very similar drug, but much cheaper. It has worked very well for me. Almost too well in that I sometimes have difficulty cumming at all. I take it the morning of the day of the punt, so at least 6 hours before. The only thing I have noticed as far as side effects is it seems to make it a bit hard for me to sleep that night, but then I'm fine the next day/night.
I agree SSRI's are not to be messed with casually, but I don't think taking one dose just on the day of a punt is likely to cause any significant problems, but that's just my opinion.
But, as I said, it definitely helps me to last much, much longer than without it....