is there a best time to harvest hemlock trees, eastern hemlock

[maple flats]

I have some rather ambishous plans this year for my sawmill, likely greater than my body will keep up with. As such, I'm wondering if it really matters when I fall the trees needed for my multiple projects as long as I store the logs up off the ground. While I set here, as it's raining outside I am wondering how many trees I should cut in the next 2-3 months. I have a good supply of 14-28" dbh hemlocks. My wishes are to build an addition on the side of my shop, a 14x32' 1 story, off one side of the shop, a leanto roof off the other side, 10'x28', a pavilian style cover for my Woodland Mills HM130Max on their trailer, open both ends to drive thru if I need to move the mill, a 12x16' storage shed, an 8x10 sawmill shop, with all of my equipment for the mill, sharpener, setter, chainsaw grinder, saws, logrite tools and spare parts and chains and maybe even a 8x18' solar kiln. The Kiln would come last because the projects will all be built using lumber off the mill in a short period of time (green).
If I tire out too quickly and I have logs on runners off the ground, do they suffer very soon or will they last a year or more. 
At the age of 77 my days are no longer 14 hrs long, in fact about 1/3 that time is more likely, and my grandson who I had planned to get to help me recently got a "real" job, he works at a pizza shop part time. I've tried over the years to hire other school aged helpers but I've never gotten much success in who I hired and my budget doesn't allow me to hire a man with family full time. The school aged kids all now seem to just play games using their thumbs. My last good helper is now in the Navy and it's sounding like he may be a career guy, as such he has 14 more years. By then I'd be 89, likely too late for any plans. If i'm still above the daisies i'll likely just be in my recliner watching others work. 

[moodnacreek]

We don't have hemlock anymore but back when I was learning we did. An old time sawmill man whose mill I often visited owned a wood lot with large hemlock and pine. It was like a virgin stand but I thinki t may of been original 2nd growth, Anyhow he would only cut hemlock in the fall and saw it before spring.  He claimed there would be much less shrinkage and splitting and that is certainly true.

[BargeMonkey]

 We cut it yr round, try not to saw it when it's really frozen. If you can skid it when the ground froze and avoid the mud that's 90% of the battle. 

[thecfarm]

Why cut the trees before they are needed?
I do a lot of cut the tree, saw the lumber and builds all in the same day.
I have cut hemlock, spring, summer and fall, Did not notice any difference.
But hemlock will keep a year easy. My father and me cut one and left it through the winter. But this was in the woods shaded too.

[Ianab]

Anyhow he would only cut hemlock in the fall and saw it before spring.  He claimed there would be much less shrinkage and splitting and that is certainly true.

Probably due to slower drying in the Winter, so the effect was real.

That (and avoiding mud) is the main reasons to consider seasons when logging. But that all depends on the species and local climate. Logging here in NZ is problematic in Winter, because the ground doesn't freeze, it turns to mud. So loggers prefer the warmer / dryer months. But I can see how a different climate would change things. 

[Don P]

With us its become cold mud or warm mud. The few that are left aren't fussy. I had to break down this afternoon and run in for a shearing. The woods just leafed out, not baby steps, we turned 80 and green. Took the cap off to cool off in the breeze in the truck and there was hair everywhere. I gave her double and made her day. I told her its kind of like a body shop, there's some jobs where the posted price needs to be viewed as just an estimate  .

[beenthere]

Suggest cutting as many as you think you can saw up during this "season". i.e. less than a year out. Log at your pace, saw at your pace. The sawn lumber will last better stickered and stacked for air drying better than stored in log form. 

[maple flats]

Thanks for the replies, I currently have 2 logs on the ground (literally) and one on the mill. After reading the suggestions I believe I'll use Beenthere's suggestion, it sounds the best for me. I'll try sawing the log on the mill and the 2 on the ground, all 3 were felled last fall, before snow was on the ground, then life happened. Originally my plans were to saw them in a few days, now about 6 months later those few days are now near. I'm suspecting the one on the mill, with 2 opposite faces off (are those called flitches?)will be good, I will see what I find in the 2 on the ground, they might be history. It just seemed too many things beyond my control changed my good intensions.

[BargeMonkey]

Hemlock can sit almost 2yrs, white pine you can get a good year but it maybe a bit blue, as long as the stuff is kind of off the ground. We have sawed some stuff that's hung around the yard way to long and didn't have issues, typically if your getting punky or shaky hemlock when sawing it was junk to begin with, 6 months shouldn't be an issue just make sure you've left enough trim to put fresh ends on it.