If you're involved in a hiring process, that is part of your regular duties. If the sum total of the things you need to get done can't be done in a reasonable amount of time each week, then it's your job to push back. Working 20 and 30 hours a week of overtime to get things done is just a recipe for inefficiency, burnout, and health problems.
If hiring activities are in your job description, then they’re part your duties. Otherwise they’re someone else foisting their responsibility onto you. This sort of doing is not uncommon. Your job might be a 40-50 hour/week deal, but management will ask more. And they’ll do it to get the work for free.
I will note that salaried positions often are arbitrary on the time commitment.
Regardless, in practice, if you're asked to do something by your management, that is literally the definition of "your regular duties." Working a couple hours overtime isn't anything worth complaining about (nothing will change and you'll get flagged as a complainer), but working an entire extra workday is. See my previous comment for reasons.
