When using an RCM exploitable Switch, you will need to boot into RCM and push the payload for your CFW each time you coldboot the system. Without hardmodding the system, CFW will not be persistent after a coldboot, unlike the 3DS.
That being said, there are things you can do to minimize the inconvenience of this. If you install AutoRCM, your Switch will automatically coldboot into RCM, removing half the steps. You'll still need to push an RCM payload for CFW though, which means you cannot coldboot your system with AutoRCM installed unless you're near a computer or another device that can push RCM payloads.
The easiest way to give the illusion of a persistent hack, however, is to just keep your Switch in sleep mode and docked when you're not using it.