I have 3 modes: getting progressively worse, getting progressively better and everyday-well. :)
When I have a flare it usually takes a month or so where I start having symptoms and then it gets really bad really fast. Then I am sick for however long and that is what I consider a flare. It's at that point that my dr puts me in the hospital with IV steroids, morphine drip, etc and I am out of work on medical leave, etc. Usually it takes about 4 months from start to finish and I am back to being well again.
This has happened about 5 times over the past 4 years, there were 2 times I wasn't in the hospital but was too sick to do much of anything so was on bed rest for a couple weeks.