I watch a complete DVD (20 episodes) in the afternoon.
But since this past June 27th, I'm regularly watching three or four (a few times only two) episodes a day (depending on how many originally aired on a given date) from five different storylines.
A complete DVD is 40 episodes and it would take all day to watch. I know because I actually did this during Labor Day weekend.Since August, I've been watching 8 episodes a day trying to go through at least one set a week.
Even though DS originally aired during the day, I find it more fun to watch them at night for the spooky factor.