It's totally up to you my friend. Your body is a highly adaptable machine, capable of all sorts of feats that might seem unimaginable. For example, the Dutch extreme athlete Wim Hof set a world record by running a marathon in Death Valley without drinking any water during the race.
He also is very knowledgeable and experienced about such things and uses special meditation and breathing techniques to achieve such incredible feats. While we don't recommend running a marathon without water, there's nothing wrong with mindfully pushing yourself if you so desire. Just be sure to exercise caution and thoughtfulness, and have a backup plan in place.
All in all, the best racing vests are a great option for those of you who want to stay hands-free and ensure that you have the storage space you need.