First I would figure out what your pitch rate needs to be. When you say go to your 5000ml flask, are talking about making a 5000ml starter for your beer? Or keep it around 3-4000ml.
Best thing to do is to make a 2000ml starter in your 5000ml flask. This should get you to about 200 billion cells. Then if you add another 2000ml on top of that you will create another 100 billion cells.
However if you start with 1000ml your cell count will increase to about 150 billion cells. And if you add another 1000ml to that you wont increase by another 50 billion, but only by about 18 billion. So you would have 168 billion.
Again figure out what your pitch rate needs to be because you will most likely not need a 5000ml starter.
Edit* It also depends on your vitality and viability or the yeast your gonna reuse..
Toasting Tortoise Brewery
- Smoked Belgium
- SOUR TORTOISE
- Burton IPA, Munich Lager, Cream Ale
- Muscadine Port, Imperial Stout
North Florida Brewers League