I know swamp coolers can be a huge pain because of all the maintenance required. Remember, the most important times for temp control are in the first 3-4 days of fermentation. If I were in your situation, I would be maintaining during that time, and then taking it out and letting it free rise. No need to keep it at 68 when the beer is done. In fact, I usually raise my ferm temps by at least 4 degrees by the end for cleanup.