I don't use them all together! I usually choose two with contrasting ink and they stay on my desk all day, doodling, making notes on worksheets, doodling again, writing useless notes on worksheets once again.
TWSBI Diamond - Sailor Rikyu-cha
Mabie Todd Swan - R&K Scabiosa
Parker Duofold (Black & Pearl) - DIY dark brown mix
Parker Duofold (Dusty Red) - Sailor Yama-dori
Noodler's Flex pen - dirty mix of blue and purple