Usually, febuxostat is taken once per day.
Sometimes people need to take more than 40mg per day. If your UA tested around 8mg/dl while taking 300mg allopurinol, you probably need more than 40mg per day. You could however start by taking 40 mg per day for a few weeks before getting a blood test and adjusting the dose based on the result.
Febuxostat has an effect very similar to allopurinol. But the amount you need to take is different.
With both drugs, you need to reduce UA to less than 6 mg/dl, ideally to 5 mg/dl or even less. And you need to keep UA there for many months (sometimes more than a year) in order to be cured. Attacks are unlikely to ever stop if UA remains around 8 mg/dl.
You can sometimes experience relief from your symptoms after taking febuxostat or allpurinol for a few days but that’s not the point. Even if the drug did stop an attack, it may cause more frequent attacks for a few months.
People typically take anti-inflammatories to get relief form attacks. Colchicine is often used in order to prevent attacks immediately after UA reductions.
Like allopurinol, febuxostat is known to have serious side effects. In particular, it often affects the liver. Most people can take it without issues but you need medical supervision when starting febuxostat. In particular, since liver problems are often initially painless, you’ll need a blood test for liver function after about 2-4 weeks on the drug.
If it turns out your body doesn’t like febuxostat, you could perhaps take a larger dose of allopurinol instead.