The sun won`t kill the ceramic coating any faster than a sealant. In fact from what I`ve seen on my daughter`s cars that sit out 24/7 in a dorm parking lot for several years, it didn`t effect the durability at all.

The killer from what you describe would be the wash routine. If it won`t be hand washed frequently, the coating won`t behave like normal as it gets dirty and "clogged" up...not to mention the physical beating from the the car wash brushes. It will get scratched up and just not bead/sheet like normal.

For this case I`d go with a high durability sealant. I`ve personally used Collinite 845 and Wolfgang SiO2 Paint sealant and would recommend either. Others you might hear mentioned are Finish Kare`s Fk1000 or Collinite 476. Never used them, but plenty of people like them for their durability.