It can be as little as five days or as much as three weeks. They will generally go into heat twice a year. Most will start their first cycle of going into heat at around six months of age or as late as 14 months old. Getting them spayed/neutered will solve this problem if you don't want to breed.
I have a basset hound too(She has 5 years and I love her) but I don't know for sure how long they stay in heat. It's not the same every time.. Last year in the summer, my dog was in heat for 2 months. Wait some time to see and if it lasts to long go with the dog at the vet.