discard because they are unusable
replace it
A type V (5) PFD is a Special use, or windsurfing PFD.
Every time the PFD is worn
offshore PFD
Type, I, II, or III PFD
Every time the PFD is worn
We do not know what you mean by "PFD", please do not use abbreviations. But the answer would be when the instructions for the "PFD" say it needs to be replaced.
Every time the PFD is worn
how many straps there are on the PFD.
Proper size and comfort. No PFD can help if you do not wear it.
Every time the PFD is worn