Usually, I'll conserve shells, so that I can use them later when they are needed. I can't understand those idiots that spam red shells and they just hit the wall. When I use reds, especially when I get triple reds, I'll use them in spaces of 3-4 seconds, rather than just spamming them. When I triple shells around me, I like to keep them around me so I can use them as a protective shield. Although, some people don't like doing this because the the shells could hit you if you get shocked, after they land on the ground.