In my mind, avoiding this situation is what colchicine is for. I never used (methyl)prednisone pills so for all I know that works as well or better. But the problem I had with NSAIDs is that they would bring welcome relief but not completely stop the attack or whatever it was.
If you count ‘the pain gets better some days and worse other days’ as one attack, then I’ve had attacks lasting a good bit more than 12 days, never knowning when I would be able to walk without crutches. And the time required for the joint to recover fully after that? Don’t get me started. I can’t prove it was gout but no one ever found another cause and it’s not because no one looked.
Colchicine may not provide immediate relief but my experience has been that if you take enough (which may be more than is recommended nowadays in your country) and wait, not only does the pain slowly go away but the joint goes on to recover fully within days.
Now this is only anectdotal evidence. Maybe I just happend to start using colchicine after I had already worked through enough of the underlying problem by improving my diet or something and that’s why my outcomes improved. Possibly NSAIDs were preventing natural healing and I only had to stop relying on them. What do I know?
While prolonged use of NSAIDs is not recommended, what ‘prolonged’ means for you and for me might be very different things. If you’re still experiencing no side-effects after 10 days and a blood test doesn’t raise a red flag such as liver markers going crazy, I don’t see why you couldn’t use them longer. You’re probably addressing the underlying cause with allopurinol so it’s not like you’re going to make a habit of taking them every day.
I have abused NSAIDs in the past but the reason I say so is that there were warning signs. If you do not get any I would take that to mean you can handle the stuff. But I’m no doctor.
As to UA tests, sure you can get one during an attack. The issue is: whatever for? Whether or not the result ends up being an outlier, it’s not going to inform your allopurinol dosage, is it? Whatever your doctor’s opinion about how skewed the data might be, would it be a good time to change your dose?
Extra data is always worth having of course. If you’re going to have blood drawn anyway, by all means get your UA checked while you’re at it.