Waste of a valuable week or good idea ?

I am 6 weeks out from A race, an Olympic duathlon. I have been doing lower volume 6 to 8 hours with loads of intensity and I have been getting really good results. I have decided that after a relatively easy rest week that I am going to do a 12 to 14 hour week of all long-ish runs and rides but all in zone 2 with maybe a few strides / sprints thrown in. After this long week I go back to a few more weeks of lower volume high intensity until i taper. I have set both run and bike pr recently in race and feel like more to gain in near term but could use the extra stamina.

My thinking about the long zone 2 week is to put a nice cap on my base fitness, allow a bit of recovery from hard efforts and cement my aerobic endurance which will allow me to handle the harder efforts better and hopefully pr at my A race.

My brief history is 51 years old, solid several year base of 400 hours per year, no current injuries, my peak early in year was a 20 hour week and very consistent with no gaps in training thru the year this year.