Where the instructions should come from
Use the care instructions supplied with the specific candle. Whoever made it knows its vessel, its wick and its wax; we do not, and we will not substitute a general rule of our own for their instruction.
If a candle arrived without instructions, its maker is the party to ask. That is a shorter answer than the one you came for, and it is the one we can support.
Why there is no method here
We do not provide a universal repair or burn-care method because we have not collected attributable evidence for one. Ember & Main runs no burn tests, and we have not found a published measurement of any care technique that we could attribute to a named source.
We have verified no technique on this subject. Repeating one here would add confidence without adding evidence, which is the failure this site exists to avoid.
What we publish instead
On Ember & Main, each burn figure identifies its publisher and we preserve documented disagreements. We have not measured how long a candle lasts in your room, or what changes it, and we have found no attributable measurement of either.