It seems to not matter if you have 4 or 400 flavors in your stash at some stage you will have to sub one for another. When you are subbing you may not get the full effect of the original recipe it may well be worse sometimes it can be better bit of a crap shoot really but in the interests of saving money it can be the best solution to try a recipe.
I sub flavors all the time as do most of us the hardest part of a sub is what percentage do I use to get something remotely vapable.
Knowing your flavors is the best way and it will come with time and testing the first thing i do when i get a new flavor is put a few drops in water and taste it for strength I then do a single flavor mix we dont all do this and I won’t go into it much because it is not what I wanted to cover in this post.
My Subbing Method
Here is how I get my start percentage (I am sure there are other ways)
I will be using Strawberry Ripe tpa and Real Flavors Strawberry (sc) as my example
First check the notes
Strawberry Ripe Tpa
Now from this we can see that the Real Flavors SB is much stronger so we need to work out a value to multiply it by to get a good starting %
To sub Strawberry Ripe with Real Flavors I use the median values to work with
1.5/5 = 0.3
If a recipe calls for 4% Strawberry Ripe and I want to sub it with RF(sc) SB the maths would be
.3 x 4 = 1.2
So a sub with no safety net would be 1.2% Real Flavors SB SC would roughly give you the same strawbery % as 4% Strawberry Ripe. I like safety nets and alway put less flavor in as a first sub I can always add more later (you can also dilute but it is a lot more work) so with that in mind I drop the % by 10% so I would use 1.08% as my initial sub value (you can set your safety net anywhere you want).
Ok so you dont have Real Flavors SB SC and want to sub the other way around here is the maths for that
we use our value of .3 we got in the first bit of maths and rather than multiply we divide
Recipes wants 1.2 RF SC Strawberry
1.2/.3 = 4
So you would then use 4% Strawberry Ripe in your recipe if you want a saftey net then drop it to 3.6% and work up.
I am totally sure there are 100 different ways to do this and others will have other methods - this is how I do it and it works quite well (most of the time)
Please chime in if you have a better way.