IMO, Spray on - Wipe off or Spray on - Rinse off sealants work really well as "Toppers" and provide really good water sheeting / beading characteristics for a relative short period but aren't likely to provide any chemical protection that you may want. I would recommend that they are used on top of your long term sealant / wax applied in a similar fashion to wax, i.e, something that needs to flash off / cure.
One of my favourite combos that's incredibly blingy is TAC Systems Moonlight (A 25% ceramic sealant with at least 1 year of durability) topped with TAC Systems Shinee Wax V2 eary 3 months or so dependant on usage and conditions. The gloss is insane, really easy to apply and makes bird poo and tree SAP a breeze to remove just with warm water from a jug. I fitted it to our Black Kodiaq and even when filthy, the car really stood out in a car park.
I will also recommend Turtlewax Dry and Shine as a great value alternative to Hydro2. It really is very durable and a bottle will give at least 10 applications if used correctly (Less is defo more - just 1 to 2 squirts per panel then rinse off).
Carpro products are indeed the bees knees IMO but i thought i'd add some great alternatives. I'll add as well, like most things, the effectiveness of your sealants et al is dependant on the preparation of the paint before application. Needs to be squeeky clean with any previous sealants / waxes completely removed. A Polish is the best way (Including full decon and clay) but just the chemical decon and a panel wipe is advised for any sealant / wax.
