Going to Pyla for lunch with some old friends - serious piss-pots! 
I believe all your friends are 'old' and serious 'quaffers'..........sorry could not resist! I obviously also count myself and BM under the same heading 
It must be a colloquial usage thing.

Round here there is a significant difference between a 'piss-pot' and a 'piss-head'.
I am sure you all fall in the latter category.