That's not being caused by the fuel pressure regulator which only prevents the pressure from being too high.
On newer TJs, you have to use an adapter that goes between the gas line and fuel rail where they connect together to attach a fuel pressure gauge.
However, the usual source of the problem is a bad check valve in the fuel pump assembly allowing fuel to drain down out of the fuel rail and back down into the gas tank. The extra-lengthy time required to start is how long it takes the fuel pump to get fuel back up from the tank to the fuel rail.
But you can avoid the need to verify the pressure tomorrow morning after it has sat all night. Before trying to start the engine, and make sure not to try starting it yet, cycle the ignition switch on-off-on (not to Start) a dozen times. Pause a second each time it's in the On position. This will prime the fuel rail by giving the fuel more time to get gas up next to the fuel injectors.
If the engine starts right away after doing that, that will confirm the problem is being caused by the fuel pump assembly. This is the Bosch fuel pump I'd install if the above test confirms what is suspected.
https://www.amazon.com/dp/B001C64PWU/?tag=wranglerorg-20
Make sure to avoid store brands like from Autozone or online brands like Airtex or Spectra which don't last long enough to make them worth installing.