HCG Mixing ?

When mixing a HCG why cant you just mix the 5ml of bac water in hcg vial? I see alot of vids where they mix in a seperate vial whats the point of that?

Also how long is 5ML of mixed HCG good for? Back when I’d get it mixed at compounding pharma it came in 4ml vials & said toss in 10 weeks… This lady says 25 days whats the real deal?

I inject 2ml BA water into the vial the HCG comes in, and I store it in that same btl.
This yields 250iu per 10iu on a slin pin.

The 30 day thing is crap too.
Keep the mixed solution in the fridge in
something that keeps out light, mine has been good for up to 90 days.

The stuff I ordered says 5000iu so it will mix down with 5ml bac water at least thats how it reads on the box. I think I’ll just mix it all in the same vial if that systems good enough for HGH Im sure its good enough for HCG. I quess Ill know if my nards shrink