I have a 30x 50 two story shop / 4 car garage and use 6' fluorescent fixtures, one over each bay and a line of them in the back and a line down the 2nd floor. I haven't changed a bulb in as long as I can remember (at least 5 years). I also have a couple of bare lightbulbs in motion sensing sockets, which are great because the light flicks on as soon as I walk in, so I don't have to go to the light switch if I'm just walking in for something quick or pulling a car in. As for bulbs going bad one thing I've seen (though rarely) is that if you get ballasts made for indoors and use them outdoors there can be issues. they're usually rated for a specific temperature range and have issues outside that range...