Wow, I could never do that. I usually play a video game for about 1 hour or 1 hour and a half at a time. If the game is really addictive I might return to it 2-3 times in one day, but I could never ever play for that many hours in a row. When I was younger things were quite different though. For example, I think I finished Shining Force II in 5 sittings, which is kinda extreme, at least for me.
My ideal Castlevania Marathon would be hooking up all my old systems and play a little bit of everything. I wouldn't try to finish each individual game, just play a few levels for fun

Not the Castleroids though - I don't wanna start playing them if I don't have the intention of beating them. And I don't want beat any of them ever again, at least not in a very long time. The oldschool vanias are fine for a quick romp though
