Clo,
This is not all that unusual. My father worked 30 years for the State of Michigan and when he retired he had over 9 months of time 'in the bank'. By law (at least during the time he worked for the state), as a state employee he was not allowed to be paid overtime. Any time over 40 hours a week was 'banked' and could be taken as part of his annual leave but it WAS his in perpetuity.
And here in California, even though my employer, Siemens, has just sent out their annual 'use it or lose it' warning about any accrued PTO (Personal Time OFF - we don't call it vacation anymore since it now include sick days as well) that you've not used, you can't really be forced to take it (I think there is one other state where unused vacation time is not forfeited at the end of the year). In fact, I can have as many as 10+ weeks (actually 52 days, as the basis of the rule is 'a years worth of one day per week') of unused PTO banked before I risk losing any of it.
I currently have 15 days in the 'bank' and since I now get 30 days of PTO plus 10 holidays per year, the idea is to 'bank' approximately 15 days per year until I retire, which, based on my current plans, will allow me to come pretty close to that limit. In essence, I'll be getting a 'bonus' upon retirement of something like 2 1/2 months salary, and at the rate of pay that will be in effect when I retire, not what it was when I actually 'earned' those days.
It's all part of the game, so if you don't take advantage of it, you only have yourself to blame.

OCU