What should be done to convert the sleeping hours into a period of meditation, yet remain tireless?
I would suggest that you gradually increase the amount of meditation that you practice each day and let the amount of sleep naturally take care of itself.
Some meditators find they need less sleep due to their meditations; for others the amount of needed sleep may not change.
The Bhagavad Gita counsels neither to sleep too much nor too little but rather to find the appropriate balance. Paramhansa Yogananda also advised devotees to live a balanced life, which includes not only meditation, but other important aspects such as proper diet, invigorating exercise, and living in a supportive environment among other things. These factors all contribute to the optimum conditions for spiritual growth.
In divine friendship,