This was my first look at this passage nearly a decade ago. I took this and worked into a larger post, which you can find here: http://lectionarygreek.blogspot.com/2011/11/mark-1324-37.html
13.25 The word for fall here (from pimp-oo) is a present tense participle used with the the future tense of the "to be" verb. This construction (instead of a future participle) is a good lesson of why you should not waste any time learning future participles. They are so rare and even Greek speakers avoided them with other constructions.
13.31 The promise of Jesus that his Words will never pass away is a ou meh construction, ie, a STRONG future denial. Also interesting is that this word (parercho-mai) appears in 2 Cor 5:17, Behold, Everything has passed away.
13.34 The word here for "puts his slaves in charge, each with his work," is actually "gives his slaves each power/authority, that is to each his work." The word here for power/authority (charge) is "exousia." We are given power while Jesus is not here to do our work.