Precious was coming in season for two weeks at a time, and we were isolating first one cat, then the other. I did not want her to have a litter at that time, but was going to continue to breed Siamese. However, this kept up, non-stop. We sent her to the vet, and discovered that she had an infection. She was still
in heat! I knew that she was coming in heat far too often, but did not expect that. We had her spayed. There is swelling when the female is in season. I think this might be comparable with the lining of the human womb getting prepared for pregnancy.
Before this time, she would remain in heat about 10 days, but I didn't take chances. I kept her or him isolated for two weeks. As I said, we took turns allowing them out of their individual rooms for love and attention.
If you're not a breeder, it's best to spay a female at about 6 months. They become very nervous, and don't understand why, so they demand constant attention and petting. And the yowling can get hard to listen too. However, she is going through more misery than we are!