Just like everyone else: hours to months. The worst and longest flares involve the spine and SI joints with a frustratingly persistent gluteal tendinopathy which can last more than a year despite treatment. The most troubling thing is trying to convince a doctor that pains which last only hours to days are real since by the time you get to them, they're gone or very minimal. Because of that it took me over 35 years to get diagnosed. I was often written off as a hypochondriac.