Interesting that you say that. I served in country in Vietnam from September 1964 - October 1965 at Phu Bai and then did a series of TAD's from the Phillipines from November 1965 - September 1967 which added up to approximately 18 months total in, over, under and around RVN. I was again stationed in country in August 1970 and med-evacked out in November that year. That totals about 31 months off and on. I can only recall being in serious, immediate danger by enemy action 3 times during all that time (good luck + esoteric job assignments). People who haven't been involved in war shouldn't take the perceptions given by movies like "We Were Soldiers", etc. as reality. Hollywood is squeezing several days or weeks of action into 2 hours and making things seem more intense than reality actually is. A freind once described combat as a ten car collision on highway 101 happening every other day, that felt more like it. Sometimes you're in the middle of it and can get hurt or killed, other times your just standing on the overpass watching or driving by in another lane.
The true number is closer to 90%. Really.