Can I keep them alive?

I don't think I have talked about it here much but I have really awful track record at keeping plants alive.  The longest living plant in our house (and until recently the ONLY one) is a gerber daisy, which is basically a weed.  We decided to live dangerously though and buy two plants and see how long I can keep them alive (so far we are up to 10 days).  We went with some succulents, which I think I tend to kill by overwatering them. 

First I picked out this donkey tail, (the tag at Lowe's actually called it a burrito plant). 



And then I also added this split rock.  Just because it was cool looking. 



Anyone willing to gamble on how long they will live?  I would be happy if they make it a couple of months!