Hiya Dan - good bed time reading...ZZZzzzzz ;)
It's not that clear on the Carlack68 instructions which I sent to you. I think the little circular set of instructions in the tub of P21S talks about water beads and water sheeting (!) and help more, but it's basic stuff on that sheet.
I have taken 2 things from the research I did before I shelled out:
1) Carlack68 is a cleaner, polish and sealant. The chemical cleaning propeties will remove all waxes, supagards, even the Carlack68 applied previously. So once a year I would say or if the wax just can't give you the depth your looking for, or the winter salts have made the paintwork "rough" (run your finger along the top of the bonnet after washing and drying). However, it's non abrasive and therefore if you have bad scratches or serious oxidation, use Autoglym or something slightly abrasive first.... My wifes car was badly swirled before Carlack, and I have to say that most of these (not all) have gone, when viewed under the flourescent light in the garage.
2) Carnuba is a wonderful wax, but it is soft. I read Autopia before I ordered it, which is quite detailed, especially one of the articles on there. In order to make it last, I would say you need to give it a couple of coats, each one removed/allowed to harden sufficiently before the next coat. So all you need is a couple of hours after washing max, split across 2 days. Once 2 coats of P21S wax are applied, I reckon you should be OK for at least 3-6 months before you need more wax again...'cos even if the wax starts to wear off, you still have the Carlack68 underneath it.
Winter could be more testing for the Carnauba - with salt etc. But if like me you garage your car at night, you'll probably need more infrequent applications.
I haven't invested in any decent car shampoo yet - I bet some are better than others...? In the menatime I am using my jumbo 5 litre Zip Wax...which ain't bad - but I'm sure someone will tell me differently -
Mr Morse?