Meaningless Stuff and Marxism

I've got things to post and figured I might as well do it as a preface to my small rant on Revolution seekers. So here are the links in headline form:
NO BILL!! Don't leave us!! We love you ever so much and no one can replace you. Literally. No one
I know this is a comic, but you don't throw Abbey Road like a Frisbee!!!! You just don't, even in make believe land. It hurts me on the inside.
Now for the Revolution seekers rant. Yay rants!
According to Marxist theory first came feudalism. I can't say with an accuracy how long feudalism lasted, but it was definitely more than two hundred years. Much more than two hundred years in my estimate. Marx then states that capitalism came second and the last phase in History (and yes, the capital "h" is necessary) will be communism. Marx doesn't say how communism will work really or when communism will occur, only that it will be preceded by the Revolution which will be followed by socialism. So, to paraphrase, feudalism leads to capitalism which will lead to the Revolution which ends with socialism and finally communism. Communism, as my Western Civ II prof put, is a bit like Paradise or nirvana. Nobody knows what it really is, but its gonna be great. The idea of communism is so wonderful to so many people that certain types are always trying to ignite or look for the signs of the Revolution. Now, here is my issue with that mind set: If feudalism lasted so long, why are you constantly looking for signs or a means to start the Revolution when capitalism has only been around for 200-300 years (if that, my math and dates are a little fuzzy)? Surely capitalism is going to last a few more centuries before it petters out and the Revolution occurs. To my mind that's far more logical than feudalism getting to last 500 or more years and capitalism only getting to last only 200/300 years. But then again I'm not a die-hard Marxist or socialist so my opinion is voided by those standards alone. Still, the Great Depression didn't bring about the Revolution and our economy is pretty close to that right now. So why would the Revolution start now and not then?