How do you use Ultradian Cycles in your daily work?

You've mentioned before that you try to include at least 1 90 minute focus block per day as part of your work and overall mission. What is your max number of blocks you can perform sustainably? Do you take vacations or extended breaks? If you knew you needed to drastically increase the amount of focus you do daily, how would you schedule that focus and recover from it? Thank YOU for your interest in science!