my SD2 has been running daily since november 2012..
average hours per day must be near 12 per day, however latterly it has been on 16 hours or so every day for about 2 months..
my idler pulley went recently, and I had lots of layer shifting, printed a new set...problem gone.
upgraded to an M3 rod...quality was vastly increased, cant over emphasis how much that one change made to the machine...
sure I level the bed,,,maybe once every 30 hours or so?
new filament spools have a tendancy to slip off the spool... i need to design a small clip to prevent this....
warping is my biggest bug , however, printing with a 5mm brim helps.. but allowing the print to complete the first layer then using acetone on the brim helps to hold it down and 'minimise' warping as much as I can...
really, I can't fault it for the money, hence the reason to buy another one this morning 
I need a new one for a job for a client and I know this machine quite well now, so it made me go for another 
couldn't be bothered with learning a new set of probs with a different printer...