I work in a place that constantly hires people who repeatedly go on light duties.

Never been put on light duties myself and I've been there 8 years.

Since I do more than my share of the physical work, will it end in a shorter career because of wear and tear on the body?

I feel like Boxer from Animal Farm.

It's almost like mind game sometimes.
You ask someone to do their job properly and they come back with "oh, I'm on light duties." Great, why doesn't a supervisor bother to tell me this?

you work at amazon?

negative

Sounds like they have learned to work the system and your employer is letting it happen.

Only way I can relate is a long time ago I went to work at a Chevy dealer and I was supposed to work under the lead tech as an apprentice but there was this old man that worked there that had physical problems and soon they had me basically doing all his work while he sat there in a chair making all the pay for the work. Guy didn't know how to do anything so I couldn't learn anything from him. Told the manager how I felt and said to either give me the job with the pay or I quit. They said they couldn't do that to him. I quit.

IMO, once you get where you can't do a job anymore, it's time to do something else.

Because just like the Misc, no one there respects you

imagine my shock, this beta, passive aggressive nu-male with more bitching.
You were clearly raised by women.
You act like one to this day.
But that's the way you like I'm sure, phayggget.

What you really need to ask yourself is if you feel like you are being compensated enough for not being a lazy POS? If that is the kind of clownish nonsense you work with, why are you not a manager? If you are a manager is there a part of the hiring process you could tweak to screen out lazy buffoons? Countless news articles talk about how clever various multibillion dollar companies set up interviews that screen out prospective employees for not cleaning up their trash after being provided a drink/snack or some other trivial task that any non-sloth would simply do as second nature.