When You have 6 full items can a new slot open up for storing pink wards?

You could make it so until about 35-45 minutes in the slot is locked. But around that time, people tend to either have or are starting their last few items. This creates an issue in getting pink wards out since you have no inventory space for them. If warding is as important as it is made out to be, why does maintaining a good vision control harder to do as the game goes on, when lack of or limited vision can be the direct cause of the end of the game? No one is going to just run a 5 item build so they always have a pink ward.