Band breakage

[barbender]

Going by hours used is a good way to break blades in the first place, imo. It kind of reminds me of the little product that was sold in the 60's and 70's as a chainsaw accessory, it was a sieve that you would put some of the chips your saw cut into. If the chips were fine enough that they went through the sieve, it meant your chain was dull🤦‍♂️ Change your blade when it starts to get dull! That might be after 1 cut, or 5-6 logs. Honestly, without a debarker I think a blade is usually best switched after about 3 logs. If you have some dirty bark, that changes things quick. 
 Probably the main two ways I pick up on a blade that is starting to dull is, first- any waves at all, and second- when I get to the end of the cut, I watch the blade on the guides and see how much it jumps forward when it exits the cut. You can also feel how much of a load the carriage drive is under when the blade pops out (especially if your mill is manual feed!😊) If you can see that the blade is pushing back a good 1/8" and feel the surge when the blade comes out of the cut, time to change the blade.

[Southside]

Look at your sawdust, if it's fine powder then the band should have been changed before that point. You want to see corse material coming out of the chute.  Also look at the band as it exits the cut, the sawdust on a sharp band will be a fine, tight, stream still in the gullet pocket.  If it's a fan or spray coming out of the cut - your band is already dull.   

[Peter Drouin]

If the blade guides are not off set some and the back of the blade is being push down by the back of the guide. That where the crack on the back of the blade comes from.
I run mine until they're dull. Riding the chair on the way back with my hand on the log will tell me everything.
Most times I sharpen  6+ times and the hard part of the tooth is gone long before they brake.
WM 1 1/4x55 T7
cutting slow will dull them faster.
Load the motor down when cutting.

[Mountain_d]

Thanks to some comments on this topic I check my blade guide bearing on the idle side and found the bearing was coming apart. One of the double bearings was missing a ball bearing or 2. I was surprised to see that as it rolled fine when I rolled it by hand. It had a tiny bit of wiggle but I guess it does not take much. There was a tiny bit of vibration when sawing and I think that may have been adding to the blade breakage. I also slowed my feed rate down a bit. So far, no more broken blades. Thanks to those that shared their knowledge. 
Mountain

[WV Sawmiller]

   I have been breaking more bands lately also but in just about every case, while the blade continued to cut smooth cuts, I could feel the extra strain and several times I'd tell myself "When I finish this cant I'm gonna change blades" then a cut or two later "Wham". I don't sharpen my own or try to keep up with how many tines they have been sharpened so I've been writing it off to normal wear and tear. The WM Service team visited me on their loop a few weeks ago and checked and aligned everything back to factory specs and the mill has been cutting great. I did my 1150 hour service today and am ready to go again.

[Magicman]

Some blades get mixed from box to box, but generally all of the blades in a particular box are the same approximate age so I may have 3-4 to break within a week of so of sawing.  Within the past couple of months, I have probably lost a box due to breakage. 

It's no big deal because blades are consumables.  I keep about 50 blades in rotation and at times I may have three boxes of 10 at various stages in the Resharp cycle.  I have an unopened box of 15 that may have the "seal" broken very soon.