It's the first time that the Border Gavaskar Trophy (BGT) will be contested over five Tests, and though it's just one match more than the four-Test series contested between India and Australia in the past few editions, both mental and physical challenges can wear players down and affect performances in a long series, which makes optimum utilization of downtime essential for lasting improvement and success.
The endurance part is a little bit easier for the home team players who are familiar with the conditions and can hop home between games to rejuvenate, but the visiting teams don't have that privilege -- making downtime planning integral to their off-the-field plans.