I live in MD, technically "may issue" but in reality it is "no issue" except for business owners carrying large amounts of cash and a handful of others (self defense is specifically cited as not being an acceptable reason to approve the application). I do have a UT non-resident permit, and I spend about 20-40 days a year in PA, VA, and WV where I can carry. When in those states, I now carry 100% of the time when in a place I legally can carry. I also carry when traveling somewhere else where my UT permit is accepted.
Now, should MD go shall-issue (don't laugh, the way the court cases are going, the courts will probably force MD to do so in the next year or so) or should I move to VA (once I get my masters next summer, I will be actively trying to get a job in VA), I will probably only be able to carry about half the time. I am a teacher, my next job will still be in education (hopefully as an administrator). If I was caught taking a gun to work I'd be spending the next few years looking through bars and I'd never be able to own a gun again. It isn't just a matter of being fired for violating my employer's weapons policy. Depending upon state law, I might not even be able to lock the gun in my car and carry to and from work (I'm not sure how comfortable I am with that anyway as it isn't very secure). So, I would never carry to and from work, during the week that is typically more than half of my trips out of the house. On weekends and on vacation I would carry whenever and wherever it was legal to do so.