Yeah, it's heavily RNG dependent. Over 175k practice points ive gotten 12 red runes: 2 x Ice, 2 x Explosive, 2 x Wind, 2 x Gale, Wood, Water, and 2 pen that i sold back.

I think the longest i went between red runes was 40 million coins, but i did get red runes 2 days in a row with only around 3 million spent once.