The easiest way to confirm that your frangipani is healthy is to squeeze the branches. If the wood is firm, the frangipani is healthy.
Also, in spring and summer, frangipanis should produce fresh green growth at the tips and lots of nice green leaves. There are many factors which can reduce the attractiveness of the crowns and leaves but the larger the frangipani, the less likely this will affect the health of the whole frangipani.