from my little knowledge I'll hazard a go at answering
1. mine in my titan 510 last about 3 cigarettes worth at most, and I change to another blank I have filled up. I refill them all 3x each then pull the wool out, bath it in hot water and dry it, then reuse, my girlfriends 901 seems to be almost the same, maybe it runs out of steam a little later than mine but produces less vapour. this may be due to my excessive deep pulls on it.
note that I probably do not fill them right up and I do use it all the time at the moment, like, excessively, and really long hard pulls so this is why it is consuming so much
juice - entirely my fault - my girlfriends 901's prefilled carts seemed to last like 6-10 cigs worth.
2. I am planning on using canned air to blow it out, but most people I have seen on here refering to this situation use isopropyl or similar forms of alcohol to clean it thru.
3. dripping on a 901 from my relatively small experience does not seem to negatively impact the e cig in any way but in the long term it is kind of obvious this may reduce life expectancy but nothing to really worry about as it gives a definate good kick and throat hit after doing this - careful not to leak fluid everywhere though of course and be careful of your automatic batteries as they may end up gunked up if you do this alot.
4. there are plenty but they are fairly scattered. you can try going to the forum index and looking for the subforum 'Model specific' (or similar) and click the DSE 901 forum. there is a forum soley for this type of e cig which may contain all the answers you desire. the 901 is a very popular first time or long user e cig on here and around the world it seems so just keep your eyes open and use youtube too, there are lots of guides, some very useful ones on the DSE 901 (also called a Totally Wicked Platinum) on youtube from ritalee, showing how to fill it up, best ways to store it, best ways to carry it around, how to use it efficiently and how to clean and maintain it.
I hope that was helpful.
last but not least, welcome to the forum and good luck transfering over to e cigs and dropping analogs if that is your intention!
day 6 here with not 1 real cig from 30-40 a day.
Happy
vaping