To quote Richard N.'s earlier post -
"Fluorocarbon DWR's are the most durable but, sustained rain and/or abrasion will quickly negate their effectiveness. My average Alaska bushwhacking distance, in intermittent rain, averages about 60 miles before the DWR is no longer effective.
"In most cases, a household dryer, iron, or hair dryer is needed to make the fluorocarbon tails stand back up and reactivate the DWR (reduced surface tension). An approximate 140F temp for about 15 minutes is needed. If this doesn’t work, more DWR needs to be applied and then heat treated."