Balancing long run benefit with injury risk
Im currently 5 weeks out from my first marathon. Goal A is under 5hr30, Goal B is just to finish strong. Ive been following an 18 week training plan and have completed most runs, barring an illness. I did a 30km a week ago, which went quite well (im on the slow side so 3hr45 at an easy pace) and I was feeling good. Rested for 2 days and then ran 10km and my knee felt pretty awful. It was a bit swollen and appeared to be a case of runners knee. I rested and its now feeling back to normal but I had planned another 30km and a 32km before I taper. Following my 30km, I truly believe i can do this race but how much extra benefit will I get from those 2 more long runs vs my likelihood of getting injured? Ive already ran 25km twice and 28km. Part of me would like to complete the 32km, so I know what it feels like to be within 10km of the finish line but will that extra 30km help or hinder? And if I do skip it, what would be an adequate replacement run?
Any advice appreciated!