That depends on the tire and how bad the tire is.
There's no way to know for sure how long the bad tire will last or how much longer you can drive with the bad tire before it bursts or comes apart on the highway.
If the tire has just cracks on it and good tread then it will likely last at least 1,000 miles or more before it goes bad but be careful and be prepared in case it does come apart on you.
Have a spare tire with you and the tools to change the tire.
I've driven for 10,000 miles and sometimes longer on tires that were weather checked and cracked although I was worried they would go bad.
I just kept a couple of spare tires with me and never had to use them but after I had wore the tread down on the cracked tires I had them replace.
But if the tires are splitting in the tread area or the tires are splitting on the sidewall or you see bulges in the tire tread area or sidewall you should get the tire replaced as soon as possible because that tire is gonna explode on you soon.
When a tire explodes while going down the road it could cause a roll over accident and can kill or injure yourself, your family or others on the road.
Tires are expensive but your life and others life are worth more than the tires are worth.
So replace the tires when needed for safety.