Due to high copper prices ac manufacturers are now using lower gauge copper pipes to keep prices affordable. The first thing that would go bad in new AC would be its cooling coils or condenser coils.
PCB should be least of concern if you are using voltage / current breakers.
Also faults in PCB could be easily repaired. For 4-5 thousand rupees faulty PCB could be repaired in Lahore.
Regarding R410A gas US made gas is being sold for Rs 1500 per kg in refrigeration parts market. But ac technicians charge Rs 4000 per kg for just gas top up. I would recommend to buy your own gas and give it to technician for top up/refill.
Also you can't trust ac technicians. They would sell chinese gas calling it US made for the same price.