Probably a long time. Though RNG could make it 2 months. Could make it 4 months. You could offset this buy buying his shards with crystals if/when they show up in Shipments. Depending on how desperate you are, there's always the shard shop, but I wouldn't that currency on FOTP
4/25/2016 - The day General Grevious Shards were reasonably priced.
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7* requires 330 shards 1/3 drop rate means with one node 330 days
Two nodes 165 days
Two nodes with a refresh each 82.5 days