The comments are already clear about the fact that male cats (or dogs for that matter) don't go into "heat" at a seasonal cycle.
In nature, it's usually the females that have a hormonal cycle and are willing to mate only at very few, specific days. The males, on the other hand, must always be ready for that rare day they find a female ready to mate. However, when a male smells the pheromones of a female, it causes excessive hormone production, which makes them more aggressive (to fight off competitors) and more willing to run away from home (to find a mate) most of the time.
The next big misconception is about the "integrity of the body". That is a big topic for humans, especially for those who had their bodies modified in any way before they were old enough to understand or consent to the procedure. However, a cat will never be able to understand and consent.
A neutered cat will never regret not being able to reproduce, because they are not capable of knowing and understanding what their life would have been like otherwise.
But an intact cat will always be aware of the fact that he's not allowed to follow his instinct to find a mate. The instinctual pull to roam the area and stay aways from home up to 3 days and nights will never go away as long as he isn't neutered.
So the real question is: Do you cause him pain for a short while by neutering him or do you deny his instincts for a lifetime.
Another misconception is about sexual pleasure in animals. This was also covered in the comments:
For cats, sexuality is not a matter of pleasure and happy cuddling, it is quite the opposite - violent and unpleasant, but they do it because it is compulsion based on the instincts; only humans, dolphins and some monkeys are doing the thing for pleasure.
As children we see cats cuddle in cartoons (I remember Simba and Nala from the Lion King), but those are human behaviors in animal bodies. In reality, Simba would have bitten Nala in the neck to hold her steady and the act would have been finished in seconds. Afterwards, he would just have walked away, no cuddling or gestures of love involved.
I dare you to research cat sex. Spoiler:
The penis of a cat has barbs just like their tongue...
Granted, the male won't be on the receiving end, but many cats get injured while fighting for a female.
I don't want to gloss over possible problems here. No situation is ever black or white, there is always something in between.
The urine of male cats that aren't neutered is very stinky. Even worse, intact cats may start marking their territory by peeing on walls and/or furniture. Neutering removes much of the smell and the instinct to mark, but some cats still continue marking even after being neutered once they started the behavior.
Every operation always comes with a risk. Cats are usually neutered under full anesthesia by removing the testicles through a small incision in the base of the scrotum. The incision is so small that it usually doesn't even require stitches but is glued shut instead. Your vet should give your cat a special pain medication for a few days after the procedure.
Most cats recover very quickly and resume normal activities like playing or hunting within 3 - 5 days after the procedure. But there can be post operative complications like bleeding or infection and general anesthesia always bears the risk of death (albeit this risk is extremely low in young, healthy cats). That's why a full bloodwork is required before anesthesia.
- Cat Neuter Surgery From Start to Finish by Pet Central
- Pros and Cons of Spaying and Neutering in Cats by PetPlace
- Neutering Aftercare by Petable