Tapering for your event
In the last week or two you ease right off, so you turn up rested with all the fitness you have built still intact. Done well, a taper reliably makes you faster on the day.
Rested beats one more big week
By the final stretch the fitness is already in the bank. One more exhausting week cannot add much, but it can leave you tired on the start line. Reducing volume while keeping a touch of intensity is one of the few things shown, again and again, to improve performance.
What to cut, what to keep
Cut the volume: your long session drops to about half of the week before. Keep a little sharpness: short, easy efforts so your legs stay lively. Plans of twelve weeks or more earn a two-week taper; shorter plans get one week.
You never do the full distance in training. The biggest session peaks near 78% of the goal, two to three weeks out. The full distance is for the day itself.
Trust it
A taper can feel like laziness, and the fresh legs can feel almost too easy. That is the point. Resist the urge to cram, and let the rest do its work.
See where the taper lands in a full build with the plan calculator.