B206 Free Wheel Unit Failure
I must agree with 'Falcon Al', the freewheel unit on the 206 series helicopters is one of the most reliable with only a (very) occasional forward oil seal change required. For example, in all my years maintaining JetRangers and Longrangers I have never experienced a freewheel chip light illuminating. Provided the initial shimming is done correctly these units will generally go to their TBO without any fuss.
However, I disagree (slightly) with the comment by 'vaqueroaero' i.e. "..If your machines are flown regularly I wouldn't be overly concerned..." Generally there is no need to fly a helicopter regularly to keep it in good shape. A ground-run every 7-10 days will usually suffice - during the run, which should include a minimum 5 minute period at 100% Nr, turn on ALL electrical and avionic systems and to the maximum extent possible ensure they perform properly.