Usually one does not reuse a candle used for a specific purpose. Depending on who you talk to this is either an insult to the powers that be, confusing since you have the residue from the previous spell(s), or just flat does not work.
Personally my belief is that if I use something for one spell then I am using the magical properties of those items for *that* spell and do not want to dilute it between several spells.
What I usually do in situations like that is to take the bits of the spell (the consumable goods and not tools and/or crystals and the like) and create a sachet out of them and keep them around.
For example I would have had him not only visualize him getting that job, but him enjoying a long and enjoyable career at that firm for as long as he wants to remain there.
That way keeping the sachet keeps the magical energies close at hand. And it's always nice to be able to pull it out and place it on the altar and give thanks whenever something good happens at the job such as promotions, bonuses, raises, etc. That way the magic is also keep up to date.
In your case however, since the two spells are related, should he get the job do the same thing but this time have him visualize the aforementioned successful career at the firm...etc, etc.
Then make the sachet and keep it for as long as he has a job with that company.