lp user permission settemp true 2592000.00
When the player has this permission , Entering again will have no effect

I hope there is something like this that can adjust the time the player has this permission

lp user permission add is 2592000.00

You can use the accumulate modifier feature for the settemp command.
See: https://github.com/lucko/LuckPerms/wiki/Command-Usage:-Permission#lp-usergroup-usergroup-permission-settemp-node-truefalse-duration-temporary-modifier-context

thank you!