Now the next logical question: Do you have chains dedicated to wood type? .
If I did more CSM'ing I'd probably set up some chains this way.
However, because 95% of the logs I cut are hard my longer (42 and 60") chains are all set up for hardwood (raker angle ~6.5º).
I don't even use different raker settings for the longer or shorter chains although I have though about doing this.
Instead for extra hard/wider wood I usually use a 7 pin sprocket instead of the 8pin.
I do have some 9 and 10 pin sprockets but have never used them.
For the times when I do occasionally have a softwood log I usually just swipe the rakers 3-4 times more than usual which increases the raker angle.
I have a 24" cross cut, full chisel, full comp, 3/8 chain for the 441 with ~9º raker angles for trimming branches off trunks. That's quite aggressive and prone to kick back - not something I let a newbie use. When milling with the 441 I use a 25" bar low pro chain set with rakers set to~ 7.5º.
Personally I sharpen as i feel the saw start cutting differently. I know very subjective, but so far it's worked "ok" .
Feel is important but by the time the saw feels like it needs an extra load to keep cutting the chain should probably have been sharpened although if you near the end of a cut practicalities indicate you just finish the cut.
On the BIL mill I can compare the temperature gauge reading with the feel or speed of cut and infer a degree of bluntness - its not rocket science - it is pretty obvious what is going on.
It's not that easy to see this effect because the temperature always increases as any cut proceeds but is more noticeable in wider/longer cuts).
Initially the temperature always increases rapidly as the powerhead warms up under full load and after about 3-4 ft of cut the temperature starts to increase more slowly.
At some point (hopefully in the second half of the cut!) the temperature starts to increase faster again and sort of steps up to a new level (still increasing) over a distance of about 1-2 ft of cut.
This is clearly the chain going blunt because after this point the mill also needs greater pressure to keep cutting at the same rate and more powder and fewer chips are generated.
At this point I open up the aux oiler a bit more and it sort of helps.
The point in the cut where this happens varies quite a bit probably due to how sharp the chain was to start with, wood hardness, dirt, dryness.
In something like Iron Bark (very hard wood) I have seen this happen around 25 sq ft.
In silica infused Tuart (this tree is notorious for sucking up silica when water deprived) it can be less. On one Tuart log I had to back the mill out of the cut and touch up the chain for the 2 wider middle slabs of the trunk. The other problem with Tuart is it's pointless pushing the saw too much past this point as the chain heat starts to extract a black resin out of the wood and it gums the chain up something horrible making things even worse. This is where extra aux oil really helps.