Yep, actually its best do it all at once because you want to keep the car as clean as possible when you are laying down the sealant layer. After you do your two coats of sealant (for best coverage) you typically let it cure over night. Clean off the surface the next day with a spray cleaner and add your monthly wax topper in either paste or spray form. After a wash don't wax the car again. Use a spray wax booster like so many that available (Dura Gloss Aqua Wax, FK 425, Z8, Mothers Reflections, etc.)
p.s. 4-5 hours on the exterior only?
Maybe if it was a Licoln Navigator!
You should be able to do the seasonal Boxster 'wash and seal' in under 3 hours and that's being meticulus.
Washing 20 minutes (including 10 minute pre soak). Claying while the car is still wet (45 minutes or no more than 10 mins per panel). Quick wash again to clear the remnants that broke loose during claying, 10 mins. So basically 1-1.5 hours of prep.
Polisihing, 5 minutes per panel. Rinse down clear away any dried up bits of polish 15 minutes, .5 -1.0 hours of polishing.
Sealing, again 5 minutes per panel. 40 minutes. The more carefully you prep the paint the easier the sealant will go on and off. So basically 45 minutes to an hour for sealing.
And you only have do all that 3 or four times a year depending on your climate and if its garaged or not.