To your taste. Chain and I are very close in height, (6'2") and in riding ability (alright, so he usually beats me, but not by much) and he does not run risers on any of his bikes, for many of the reasons listed above. I run 3.5" risers on my Big Red Pig, 2.5" on my DR650 and KTM 250 and have found that it improves my ability to lift the front, and definetly lets me ride longer without the back ache.
At the suggestion of Brian Crawford, I tried a 30mm straight rise on my Gasser. I found it improved my comfort, and improved my ability to steer, not really sure why. Only time they have caused me any issue is very large vertical faces, where you have to fold over the bars to get the front back down. I end up with bruises on my hips, though I am not sure I wouldn't have them anyway with risers or not.
So, try it. If it makes you more comfortable, you will have more fun, you will ride more, you will get better. As mentioned above, I also roll my bars pretty forward, to lengthen the cockpit. +1 on tall workbenches. Pisses off my wife, but keeps my back from cramping when working.
ATGATT: When you fall off your motorcycle, you will be wearing what you were when you got on your motorcycle. Dress accordingly.