Possible Pebble Time disconnect fix for the Nexus 6 running Marshmallow.

Is your Pebble Time disconnecting from your Nexus 6 quite often?
Android 6.0 (Marshmallow) introduced a feature called Doze to conserve your battery life.
Whitelisting the Pebble Time app may resolve your disconnect issues.

1) open your notification tray
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2) click on battery percentage
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3) click on the 3 dots in the upper right hand corner
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4) click on Battery optimization
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5) click on the Not optimized drop down
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6) select All apps
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7) scroll down and select the Pebble Time app
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8) select Don’t optimize and then select DONE
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9) the Pebble app should now appear as Not optimized.
Screenshot_20151211-114846

That should resolve your Pebble Time disconnect issues.
If it does not additionally add the Android Wear app to the Not optimized list by following the above steps.
Good luck!