If everyone start storing bitcoin and there is no single transaction for days,all miners will quite mining as without transaction there would be no reward.
Will it not kill bitcoin and make it useless?
if users will totally keep on storing they bitcoin and doesn't make any transactions then it will surely bring on the bitcoin ecosystem because bitcoin needs to circulate in order to keep the network to operate I guess . but anyway, because in this community many people are often using bitcoin for various purposes such as trading goods for bitcoin, gambling, trading etc. so it is really impossible that there will be no transactions every single hour or day .