“If I let you go for 30 days that proves I can live without you for a month and that would prove I can live without you, period. Since I can't, leave is denied. Write it for a shorter period of time.”
I had a similar experience stateside.
At my last office at the Pentagon before I retired I was one of the two lowest ranking officers. I was a Captain in a LtCol billet. Anyway, they relied on me to do a lion's share of the work because I was the only one there with degrees in Engineering and Physics and they dealt with a lot of technical things of which they knew nothing.
While I usually worked 60 hours per week or more (one week I actually worked 104 hours and lived in the office alone) they would take time off, go golfing, and take leave. I would schedule my leave times four months in advance with their approval but they cancelled every single leave about one week prior using the excuse that they could not live without me.
I was so tired and jaded that when I received my line number for Major I instead put in my retirement paperwork and left at the 20 year point. I never looked back and made them mail my Defense Meritorious Service Medal to my home because I did not want a bunch of two-faced liars to attend my award ceremony.