It is my goal to nurse for one year. It's not an arbitrary number that I've chosen, it's the age babies can drink cow's milk. So if I can reach my goal of one year, I won't have to use formula. At least, that's the plan.
I rented a Medela Lactina from the Lactation department at St. Vincent's Hospital, where I had Little Man. It's a double electric pump. It's pretty loud, but it was the only one they had. It works well though, and it's a convenient size and shape that fits on my desk at work, discreetly tucked behind my computer screen. I carry it back and forth from home to work every day.
It is federal law that your place of work (if it employs 50 employees or more) has to provide a reasonable amount of break time (unpaid)) and a place other than the women's bathroom for you to pump. My office at work has a door with a lock on it. I pump three times a day. I work from 7am to 5pm, and I wake up and feed Little Man at 5:30am, so I pump at 8:30, 11:30, and 2:30, and I nurse when I get home in the evenings. If my supply gets low, I use the pump in the middle of the night.
Milk supply seems to be the biggest issue you face when you use a pump while away from your child. A baby is more efficient than any pump, so your supply will naturally dwindle. I take fenugreek (you can get it at Babies R Us), and while it won't increase my supply, it does help me to maintain it. I also noticed that snacking and drinking water between every pump session improves my expression substantially. The biggest suggestion I have is to never use a bottle on the weekends. Even if it's really inconvenient, nursing on the weekends and after work is the best way to maintain your supply.
My biggest obstacle is work travel. I often have to travel to jobsites during the workday. These are construction sites with no place to pump and no power. If I have no other option, I use my Medela Harmony manual pump. I try to find a bathroom but most of the time I end up in my car. The manual pump is not nearly as efficient, so doing this a lot can harm your supply. Medela makes an adapter for your car to plug your pump into the lighter. They make a battery pack as well, which I have not used but might be convenient for you.
And then there's the social issue. I work with men, all men, no women. So that means that sometimes when I pump in my office with the door closed, someone knocks and yells, "what are you doing in there?" Or I disappear for 10 minutes while I'm on site and everyone asks, "where'd you go?!" The only way I've found to deal with this is to joke about it. "I'm a mobile cow for my little one!" If you tell people what you're doing once, they won't ask again. I also keep a Pack-it lunch bag in the fridge or freezer to keep my milk bags or bottles in. That will keep any office guests from picking up your milk thinking it's coffee creamer (yes, this happened to me, fortunately I was there in the breakroom when it happened and was able to keep the dimwit from drinking it!) And if I have to travel, the bag is freezable so it keeps the milk I pump while I'm out of the office cold for a couple hours. If I'm going to be out all day, I use a small igloo cooler with an ice pack in it.
So that's how I do it. At first I was embarrassed about it and skipped a couple pump times because I didn't feel I could tell the people I was with what I was doing, but after becoming severely engorged a couple times, I got over it. Don't do that, it hurts quite a bit more than you'd expect. It actually hurt so badly that I couldn't lift my arms. And you can get plugged milk ducts, which are even more painful. If, for some reason, that happens to you, I tried every trick I read on the internet, but the only way I found to unplug it was to use my hand pump and hold the handle down for a minute or so (until milk starts coming out again.) You'll know when it breaks loose, your milk will suddenly gush out. This hurts a lot, don't get me wrong, but it's better than mastitis. Better to just get over your embarrassment and be proud that you are dedicated enough to go through so much for your child!
Good luck and happy nursing!