Initially, full-time wear of your retainers is critical because the bone and muscles are adjusting to the new positions of your teeth. You must wear your retainers essentially for 24 hours a day for the first 6 months and only remove them for eating, drinking and cleaning. Then you would have to wear them every night for another 6 months.
In the long term, it is advisable that you continue to wear your retainers for at least 2 nights or more a week forever! If you do not follow this instruction, there is no guarantee that your teeth will remain beautifully straight. The responsibility is yours!