Being 'Old School' makes it difficult to hold my tongue at times...

Six years ago I started a new job after staying at home for a year following taking an early retirement.
I didn't like staying home and figured the new job would help finance my '69 Dart build.
I found something I wanted to do and was hired immediately following my initial interview. I'd previously spent over 25 years in management but didn't want to deal with the hassles of management any more.
Today (Friday), the COO is on vacation so our manager said we can knock off work today 2.5 hours early. I heard him tell someone else he's heading to Las Vegas after work.
There's only 3 of us in the office today so, being 'old school' I decided not to take my lunch break today and work straight through to the early quitting time.
The other guy in the office ended up leaving 1.5 hours before the early quitting time...taking his lunch break plus an additional 30 minutes and nothing was said.
If I was still 'management' he wouldn't have done that and we would be here for the full day.
I know it was my choice to work through my lunch time, but it's difficult watching others not give a full days work for a full days pay and then also taking extra time.
Rant over.
Thanks for listening.