Time can indeed be beneficial to a clear finished beer but process is more important. You should be able to get a clear ale in under 4 weeks if you follow good process. I'll say extract beers are harder to clear but there are extract brewers who will likely disagree.
As to process...Use a fining agent like Irish moss or whirlfloc in the last few minutes of your boil. Chill quickly to drop out the hot and cold break, then whirlpool to keep most of the trub in your kettle as you siphon off to the fermenter.
The last part is less important to me but some brewers feel otherwise. After active fermentation begins to slow down let the temperature of your beer rise for a D rest. Then prior to packaging cold crash to as close to freezing as you can get for a day or 2. Rack carefully beginning high and ending low but avoiding the trub in the bottom of the fermenter. if you're kegging the cold crash is less important as you'll do that in the keg but doing it before can keep some trub and yeast out of your keg.
A week or so at cold temperatures in the bottle or keg and your beer should be clear.