OK, so I know the answer is to get a huge ladder, but I'm going to ask for experiences anyway. We have a two-story foyer with a changelier and a window near the top. Both are positively caked with dust. Is purchasing or borrowing a death-defying ladder the best way to clean these? Would I be better off hiring someone?
My parents house had a picture window above the front door (like way above) and a pendant style globe lamp in the ceiling that was 2 stories up. As much as they didn't clean, they would have us use a telescoping duster to get all up on ledges/the lamp and the walls once in a while and about once a year (or whenever the bulb went out) my father would get up on a big effing ladder and wash the window and they'd wash the globe in the sink before putting it back on over a new bulb. Yay for 2 story entryways (this and having to paint walls above open stairwells in the past is what made me happy to buy a 1 story home and made me never want to deal with a ceiling taller than 13 feet when renting).
If you want to avoid a ladder, you should hire someone to clean it the first time since it's caked on (tons of dust falling from above, not fun) - then after you can keep up the cleanliness with a duster in between cleanings (if you dust the area somewhat regularly you should be able to get away with a real cleaning only once every 6months-1 year or more depending.