Based on a conservative estimate, if I watch the whole series from start to finish without a break, it'll take around 95 hours. Factor in sleep and whatnot and I figure it'll be weeks and weeks before I get through the whole thing.
I've just finished watching the first few episodes and I just have to say that what I love the most about B5 is that it was one complete storyline. It's fantastic about how statements in the very first episode like Londo's prophetic vision actually come true in the last season. It's great that Sinclair's little flashback of the line ties in perfectly, including the exact same voice clip when we find out more information later. It's nice to have a series that at least feels like it was written as a complete whole instead of built up like a patchwork quilt.