Age by itself is usually not the most useful way to evaluate this. At 42, the bigger question is how your experience maps to the role the firm is actually hiring for and whether your level, compensation expectations, and story make sense together.
For an experienced candidate, firms will care about the evidence that you can transfer into consulting: leadership, structured problem solving, client or stakeholder influence, commercial judgment, and the ability to operate in ambiguous environments. A strong senior profile can be attractive, but it may not fit neatly into the same recruiting path as a 27-year-old MBA candidate.
You should also be realistic about level and lifestyle. If the firm would bring you in below the seniority you currently hold, you need to decide whether the learning, brand, and exit options justify that tradeoff. The job can also be demanding in ways that matter more at 42 than they did at 25.
So I would not self-reject because of age. I would first clarify the likely entry path with recruiters or relevant consultants, then decide whether the role itself still makes sense for you. If the answer is yes, prepare seriously and let the firm make the decision.