Based on all of these wonderful comments, how fast can a military go through 500 of these?
First, even advanced MANPADS like the Stinger missile have a very constrained scope of engagement, primarily helicopters and CAS aircraft in your immediate proximity due to the limited range. Situations where you can use them don't occur all that often because adversaries have a limited number of these aircraft to cover a lot of terrain. You need to be in the middle of a ground attack or staked out at an enemy airfield, and they run patrols around airfields to make sure someone with MANPADS cannot get within practical range.
Second, many wealthier western militaries expect to be able to suppress the kinds of aircraft that MANPADS are designed for with conventional Air Force and air defense assets; MANPADS are what you use when the adversary has a dominant air attack position. If the US or NATO ever finds itself in a position where some adversary has established clear air dominance or outright superiority, a great many things have gone horribly wrong. The only time MANPADS might be useful is clandestine or covert missions where there is almost no air support at all because you aren't supposed to be there.
The US maintains a large inventory of MANPADS, but mostly for situations like the Ukraine where an ally that has no ability to establish air superiority needs to suppress the ground attack assets of someone that does. Being able to airdrop a large number of MANPADS in a very short period of time is helpful in this scenario.
Most countries do not maintain a massive inventory of MANPADS, there is no use case for having that many. There have only been 70,000 Stinger missiles produced globally over the last 40 years and quite a few of those have been used up in various conflicts or are well past their shelf-life. Most countries with decent militaries have hundreds or thousands. Due to the shelf-life, maintenance, and obsolescence issue, it is rather expensive to stockpile a massive number of MANPADS if you don't expect to need them soon.