There seems to be a fairly consistent theme in regards to marathon training that you shouldn't run more than 35-40km for your longest runs leading up to a marathon. The reason I see repeatedly is that it will increase your chances of injury. I feel this is very much a "Bro Science" statement without any real scientific backing and that you would actually benefit on both a physical and psychological level by running further than the marathon distance in several of your lead up long training runs. Would be interested to hear anyone elses thoughts/experience on this.