I notice some degradation in my flying skills in general after a week off. Instrument proficiency degrades very quickly, and it is difficult to maintain if not practiced on a very regular basis. Most EMS operations simply cannot allow pilots to maintain instrument proficiency, because it requires a safety pilot, and you can't do it under Part 135. This is difficult area, and cost is always an issue, whichever side of the argument you're on. Flying over water at night should be avoided at all costs, unless you're in an IFR machine and IFR current.