Aircraft Technician reported PSU units with O2 generators were not being processed as a HAZMAT part and were being improperly tagged without the proper shelf life information.

Narrative

On Day 0; while working at Parts Receiving; noticed a box of PSU (Passenger Service Unit) panels with O2 generators. I asked the storekeeper if they need inspection tags. Person told me no; the computer software system is designed for these parts to go right to binning after they process it. I told the person usually PSU panels have a shelf life; also HAZMAT if it has a O2 generator or not. So to put shelf life; need a tag. In this case; goes right to bin without a tag. I looked at the stock balance and it shows shelf life 180 months and HAZMAT part; tag- X- inspection -X. I told the person to hold the parts and notify Lead to find out if it needs a tag. Very next day the record was changed to show inspection Y" & tag "Y" but still show shelf life 180. Per GMM (General Maintenance Manual) it should show "999;" which means have to go look up shelf life items; including vital information in notes pertaining to the part number. Notes say if PSU has O2 generator; need to get the part number off the generator and go to Work Order to find out what the shelf life is. Some may have 12 years and some may have 15-year shelf life depending the part number of the generator. Then shelf life is calculated to the lowest date on all the generators in PSU. This will not happen when you put a generic shelf life such as 180 months. PSU could end up with a 15-year shelf life when actuality; generator may expire in 12 years; 3 years out of date and expired generator could end up in bin or plane.By looking at the aviation maintenance software history it appears the stock balance is changed on shelf life and HAZMAT; including tagging requirements by 3rd party individuals; probably have not much experience in aircraft parts.At this stage; company is looking at getting rid of inspection from all receiving parts and give that work to storekeepers; Person A as a Quality Control Inspector is very concerned if that's the right decision. If I did not happen to walk by those parts and asked questions; would have gone to bin without a tag with no shelf life. Even if the shelf life shows does the storekeepers know how to read notes and go to appropriate Work Order and tag the shelf life correctly? Currently the stock balance shows a generic 180 months instead of "999." Violation of GMM."