Finish will last 12 months with Royale, washing to keep it clean will take a lot less time and look good afterwards.
Lets also not forget, what was done here is no more or less than some have done on older cars, adept for lesser money but the owner is also protecting his investment, high grade carnauba does set like concrete and so offers protection from the elements, not stones though so the bodywork will last longer.
Removing up to 8mu, from a car with a normal 60mu clear coat thickness does sound a lot however if the car is well cared for and properly washed if this same job was booked next year I would expect to see no more than 4mu removed, the following year 3-4mu dropping by about 0.5mu a year there after so you can see, even in 5 years you will have removed less than 25% of the clear coat, how many people keep a car over 5 years? the paintwork will look as good as the day it was first looked after, therefore sell easier and hopefully more than most of its age, thus recovering some of the expense.
Lastly yep its an Astra, however and sorry for this no offence meant, but it could well have been a case of oh its only a Seat, or a VW, or a BMW etc the manufacturers name counts for nothing even a ferrari is only a ferrari it has 4 wheels an engine as does a Citreon 2CV