Concerns about replacing a worn out light switch
Big box stores definitely carry different grades of light switches ("standard duty", "heavy duty", "commercial grade", "medical grade"...), but I can't attest to their relative endurance. For what it's worth, I've seen several light switches fail, so it's not like this is some freakish event. 3 years seems a little quick to me but of course these things are somewhat random and "the plural of 'anecdote' is not 'data'".

I would tape the switch off so that nobody uses it until you can replace it. Once you get it out of the box you may be able to see what the problem is... could be faulty wiring / a loose wire nut. If that's the case, you might want to give your electrician a call to scold them. Otherwise I would just write it off as an earlier-than-expected failure.