Redpoll feeders

I have a similar question as I have in the fall - How long to keep putting out hummingbird feeders?  There is a lot written about hummingbird feeding longevity - i.e. Keep the feeders available for at least two weeks after you've seen your last hummingbird.   While hummers won't be back here until Mother's Day, I currently have the issue of redpolls that should soon be headed north to their Canadian nesting grounds.   Redpolls love thistle seed.  The summer birds here eschew thistle seed in feeders.  To complicate things when that seed gets damp it starts to mold and needs to be tossed.  So, when to stop filling the feeder w/ thistle seed?   Not as much written about that as w/ hummers.  I haven't done well trying to think like a bird in the past but if I were about to take a long journey w/o knowing where my next meal would be found, I'd  want to eat well before taking off.   Filled up the mesh thistle feeder plus put out a sock feeder plus a block of thistle seed.  The birds have attacked all three.  Am still filling the sock & mesh feeders daily and the block has been whittled down so much it looks like a rat carcass hanging from the hook.  Hopefully the birds will soon carve it into a different shape.