I would finish my 8 pounds key then dump all the 1 lbs same lot into the jug. I don’t like mixng powder, but this is me.
I wouldn't bother.
I know where you're coming from but sooner or later that original keg is going to run out and the OP is going to have to develop a new load, MAYBE. New cannister grade powders are quite consistent, especially those as popular as Varget.
OP, just blend everything you have of VARGET into the one big container and mix very well.
I have several similar kegs of powder, including one of VARGET that I do exactly what you are asking about. I don't keep any aside. That's just a recipe for something to go awry with the load. Nothing dangerous, just to easy to mix up and lose a hard found sweet load.
Usually, when one of the tubs gets down about half way, I start looking for that powder on sale or at least reasonably priced. It doesn't matter to me which lot number they are. They get mixed into the large tub, no matter what.
From my experience of doing this for over three decades, it just make things so easy. I've never had a batch of powder need the accuracy load changed, in the rifle it was developed for, since I was first turned onto the practice.
I even do it with different lots of surplus powder of the same designation, simply because there can be some close to extreme variation between the lots, depending on what that particular lot was ordered for.
I'll give you an example. I was gifted several pounds of Canada Ammo's version of 4350. This powder came from three different individuals. All of it was in one pound containers.
Some of the containers were full, unopened and some were partially filled. I believe there were three different lots, simply because they looked different from each other.
I knew the fellows that gave it to me and there was no way they put other powders into those containers. They're all getting long in the tooth and down sized to lighter/less recoil firearms.
I ended up purchasing their brass/bullets and they threw in the powder. They used to regularly group buy.
I now have just over 11 pounds left of this 4350 type powder, all with the same burn rate, which is significantly slower than my cannister grade IMR4350. No, I'm not going to blend the cannister grade with the Canada Ammo brand.
You need to be careful when blending powders of the same designation.
H4831 is not the same as IMR4831 or the old surplus type 4831. I'm not saying they will create a dangerous situation, but if one of the older powders is deteriorating, you could lose a lot of powder. You likely won't have this issue with modern powders.
Another very knowledgeable CGNer, Ganderite, could explain this much better.
Blending several different lots of the same # designated powder, from the SAME MANUFACTURER is a good idea, all the way to the range.