It depends on several factors. I managed to cut down my moisture in there by putting the temp sensor in a beer bottle filled with water. That prevented the coils from kicking on so often and that greatly improved my humidity situation.
As for the bilge fan I would definitely say that's a must in a coffin situation. Not for humidity as much as moving cold air to the taps. I keep my keezer in my garage which isn't well cooled at all. My bilge fan pulling the cold air up from the bottom and pushing it thru pvc surrounding the tap innards and beer lines keeps the taps so cold that when I open the garage door they actually develop condensation on them, like a glass of ice water left out by the pool. It really helps. Now I wasn't able to use the little AC adapter I mentioned before but a little Radio shack visit and some help from P-J and the web got me hooked up with a step down transformer and a bridge rectifier that have been running it nonstop for 3 or 4 months now with zero issues.
On Tap: Bigfoot's Barleywine Ale, Boulevard Tank 7, California Steam
Waiting: Hard Cider, Pumpkin Ale, Black Hills Porter
Ready to brew: Autumn Amber Ale, Smooth Nut Brown Ale, Black Hills Porter
Primaries: Peppercorn Rye
Bottled: Beaujolais, Cabernet