Not really. I can visit conferences, apply for new gigs, market research... There are limits, but if you are not greedy, it is perfectly fine. Bringing gf, renting cars, beach stay... would ruin it.
It varies by trip but if I take a business trip somewhere interesting I'll routinely tack on some personal time. But, even if I'm not adding days, I'll try to make a little time to explore a place.
