I have a yi xing pot I'm using for my less fragrant oolongs. I tend to brew any new tea in a gaiwan for the first sample, just to get an idea of it's flavor, etc. If it's less fragrant ( my favorites actually, not a big fan of the more floral oolongs like ali shan, etc ) I move to using a pot.
Time wise I generally do a quick rinse ( if I use a pot I warm the empty pot first ), then immediately brew. I taste the rinse to get an idea of brew time, then pour the rinse water over the outside of the pot to help keep the temp up. I find each tea varies in time to my taste, but mostly it's around 30 seconds as a starting time (up to 50 seconds depending on the oolong). Then I add 10 seconds every brew after that, usually brew 7-8 times per set of leaves.
Sadly my supplier (floating leaves tea) is now out of that particular roasted Shan Lin Xi so it's back to drinking Li Shan and Bauzhong.