
Blackmailers don't have "seasons." There's no such thing as a legitimate writer or essay company that provides good work during the busy (writing) seasons and then shifts to blackmailing "mode" during the slow (writing) season. If their business model is building a clientele of satisfied clients by providing good work, that's what they do year-round. Conversely, if their business model is blackmailing, that's what they do year-round, not just during slow periods.
One thing you can definitely do to reduce any risk of blackmail is to simply use a writer who doesn't mind disclosing (and proving) his full name, location, and contact information before payment, especially in the US. Blackmailers can only succeed to the extent they're anonymous and/or located outside the jurisdiction of reliable law-enforcement authorities.
Nobody located anywhere in the US, for example, could possibly pull off a blackmail scheme against a victim who knows his real identity, because all the victim would have to do is report it to a state DA's office or to the nearest FBI field office.
The same goes for essay companies, except that there have been instances detailed (elsewhere on this forum) where an essay-company writer went rogue and perpetrated blackmail on a client whose project he or she had provided through an essay company.