Well, I suppose it all depends on how bad your symptoms are. I should think that if they were bad enough to send you to the doctor, then they are something to address. The type of spondylitis does make a difference. If it is primary ankylosing spondylitis, then the risk of severe spinal progression is greatest. I have enteropathic arthritis, that which is related to my IBD, so less likely to cause spinal fusion.
That said, before I started biologics I often had to walk with a cane, and I seldom do now. But, it has not completely been stopped. I now have neck involvement that was only minor 10 years ago. I have more advanced spinal stenosis in my c-spine now, and have to be careful about not hyperextending my neck, and have to bring a pillow to the dentist to be able to tolerate the dental care.
For me, the benefits have far outweighed the potential risks, and here is why. My symptoms were real and having a real impact on my current life. Side effects that have not happened have no effect on me. Most of the side effects resolve if you stop the drug and that is why they monitor you. So, I figure I made an informed choice. I could get lymphoma no matter what I do or don't take, so I don't worry about it. I focus on the fact that most people do NOT get side effects.
Yes, pain and stiffness is pretty much your guide to how you are doing. Fatigue levels too.
If you are uncomfortable with the biologics, it makes sense to try other options before you consider them. That way, if you do wind up using them, if they do not work or cause side effects (causing you to stop them), then you can feel that you tried everything else first. But, it appears that they are the new best thing, especially for those who cannot tolerate NSAIDs. I took NSAIDs for years, but had to give those up due to side effects.
Jan