A bit of this, a bit of that; mostly Turkish tabac
I have a bottle which I use to fill my tank.
To that bottle I usually just add some more of something when I feel like; so that bottle contains some of the old plus some of the new.
Its like you've got a pot o soup in the kitchen, and while it's cooking people come along and fill up a bowl, so when it's half gone, instead of waiting for it to all go, just add some more STUFFF.