There is quite a lot about Hickaman lines here
http://www.macmillan.org.uk/information-and-support/treating/chemotherapy/being-treated-with-chemotherapy/central-lines.html#tcm:9-45758
I dont think you should worry about it too much
if you wanna punish yourself read this
http://bestbets.org/bets/bet.php?id=1976
and that puts a number on the idea of " leave a hickman in long enough and it will get infected" This accounts for you knowing a lot of people with hickmans who got infected
and it is 1 per 100 catheter days
so if three patients had one in for a month ( 3x 30) you would expect one hickman infection in that time.
strikes me as being kinda high to be honest
getting one within seven days of insertion sounds like bad luck as well
anyway I think you need to wait and see and not get too worried