Sant Mat says to meditate 2.5 hours a day because real meditation does not start until the brain and nervous system move through several deep layers. The first 30 to 60 minutes are mostly beta and alpha brain waves, which are just thinking and light relaxation. The next hour drops into theta, where the body starts to fade and attention pulls away from the senses. After about 90 to 120 minutes the brain reaches delta, which is when the feeling of being in a physical body disappears and inner light and sound can appear. Short meditations never get past the surface layers.
This is why Sant Mat focuses on long, unbroken sittings. The inner stars, sun, moon, and other visions only appear when awareness stabilizes in those deep brain states where the senses shut off and consciousness turns inward.