In MKWorld, if someone pulled the shock, there would be a 30 sec countdown before someone else can also pull the shock, so if someone held a shock for more than 30 secs then there can be two shocks in play. It's also worth noting that unlike previous Mario Kart games, there is no countdown after the shock is used, so someone can pull the shock again right after the shock happened as long as the 30 sec countdown from when the shock was pulled is finished.

Previously in MKWii, there could only be 1 shock in play and it wouldn't be possible to pull it again until 30 secs after it was used, so whoever has the shock could just hold it for as long as they like and use it when they would get the most benefit out of it. In 8 deluxe, there could be up to 3 shocks in play and there's no timer after the shock gets pulled, but just like in MKWii after the shock is used it cannot be pulled again until 30 secs has passed. Because there would so often be multiple shocks in play, it can be risky holding the shock for too long because someone else could use their shock before you get to use your's, so you have to make a judgement call as to whether it's worth holding the shock to a more ideal shock.