The general consensus is that most muscles work pretty much the same
Every set of work which brings you near muscular failure is more valuable than a set of 80 reps but maybe you could've done easily 200..you just stopped at 80 because it started burning a lot.
Real failure is when you have a gun to your head and you will be shot when you stop lifting, in such situation real strength shows.... And it's not that much.
For example a person who can do 20 pull ups for real failure might be able to do 15 to 17 pull ups max normally...
So you just need to see if when you do those side raises you are getting close or not to failure.... If you do them until you get a pump or burn, that's pretty much a waste of time.
The exact number of reps matters nothing whether you get near failure with a set of 5 repetitions or a set of a 100...the results are the same....
Although some studies suggest that less repetitions and higher weights can give you more gains, about 0.1% more.
Have a good read
In the end either you do 1 rep or 1000 repetitions, it doesn't matter.... It's all about the number of "hard near failure sets"
So the question then is how many sets do you need to build muscle?
Citing Mike Israetel on this one, he suggests that most muscles only need about 3 to 5 hard sets per week to maintain muscle for already trained and experienced athletes.... For newbies this is enough to cause growth, but for real athletes it's barely enough to not lose muscle.
So for someone with at least a little bit of muscle mass, 8 to 12 sets per week tend to be the minimum to GROW muscle, why the the 8 to 12? Because everyone is different...
And not just genetically, some people might have worked particular jobs during their life, like maybe a mechanic and while they didn't develop much muscle mass, they did develop a different resistance to stress and a different muscle fiber type.
Usually muscles with slow twitching muscle fibers need more sets to grow. That's why the myth of some muscles not being able to grow exists... Like the wrist or calf muscles, because to grow those muscles the MINIMUM work needed is incredibly high depending on the person.
now you know the minimum to grow, is there a maximum?
As for today there has not been found a precise limit for how much weekly training is too much, it's seems that the more you train the more you gain.
Except if you do it all one day, spreading the work across the week let's you train a lot without and gain a lot, but doing something like 20 or more hard sets in a single day might not only damage you but actually kill you.
Obviously based on your experience your "daily limit" can be lower or higher, for example a beginner would go to the hospital after 10 sets of squats in a 1 hour.