@mrpipes answer covered it pretty succinctly.
The key (and hardest part) is finding your balance.
If you SF test from the start (as you are acquiring your flavors), you’ll be less likely to have to try and play catch up… But my general rule of thumb is: Try and have as many testers going as I do mixes.
If I’m mixing 4 recipes, then I’m mixing 4 SF testers at the same time (usually more, because I’m still playing catchup from not being able to buy enough bottles to start with.
But, because you’re not going to know what percentages you need (prefer) for a single flavor when testing, that means you have to do 2-3 bottles for each flavor.
IE: when testing FW, I’d mix a new flavor at 4%, 6%, and 8%. For FA, I typically do one tester at 1%, and another at 3%.
So even though you’re only SF 4 flavors… You can see how that quickly turns into 10-12 bottles. and that’s in addition to the 4 “recipe mixes” that you’ve got going to simply “feed the habit”.
No ‘exploratory’ (experimenting) mixes even considered yet, and you’ve already got 14-16 bottles going. Then, if you want to try something new… That may be another 2-3 bottles (or more). So it’s easy to end up with 20+ bottles in one mixing session, for just 4-6 recipes, and 4 SF tests.
But you have to find what works for you.
The most important thing is making sure that you have enough to feed your daily requirement. (Not only so you don’t run out, but so you don’t dip into your testers before the planned testing points.)
The second most important thing (having learned the hard way) is make sure that you vary your profiles when selecting mixes and testers*! Or you risk getting burned out. Both your palate, and your frustration level with mixing! (EG: don’t mix all heavy flavors for SF testing simultaneously! Like butterscotch, caramel, brown sugar, etc. Your palate will be screaming for something different by the time you’re halfway through that few weeks or month of testing, and you’ll be miserable and get really frustrated with “this isn’t working at all”.)
*the exception to this rule is when you reach the point of doing a “shootout”. Where you’ve reached the point of knowing what percentages of SF you prefer for each brand/variation of say caramel.
You then mix one tester of each, at your preferred percentage to compare the profiles side by side. This gives you a chance to refresh, and either reaffirm your earlier notes (from SF tests) or update things you might have missed, or forgotten.
But regardless, I still consider this a part of single flavor testing (just narrowing down what you’re wanting to keep/eliminate for the long haul), and as such, when I do a shootout, I still mix a batch of SF testers (again, previously untested flavors) along with the shootout flavors, and in addition to my “daily needs” mixes.
So… You can take any part of this, all of it, or practically ignore it and blaze your own trail! But this is how I’ve approached things (since you asked).
What do I think? Well, in one sense, I feel like I’m way behind my “classmates” that started at the same time, in relation to releasing recipes.
In another sense, I take solace in the fact that I know the flavors I’ve tested this far very well, and that when it comes time, I’ll be able to simply “think about” what sounds good, and be able to ‘insta-create’ a recipe that’s at least 80-90% of where I want/expect it to be, on my whim. (There’s always a refinement phase, as well as the rare ‘this flavor doesn’t chemically play well with others possibility’ to deal with or adjust for).
And lastly, I’m proud (right or wrongly so) that I haven’t “polluted” the public ELR database with recipes that are anywhere from crap, to “eh, it’s not bad”. As IMO, that’s the single biggest problem (and disservice) to new mixers. If more folks would put their pride aside, and not worry about “look what I mixed”, or some race that doesn’t exist…and keep those recipes private, new folks would have a much easier time finding at least a “good recipe” to begin with. But again, it’s all relative.
I hope my long winded rambling enables you to pull some tidbit(s) out, and have an easier road, or better understanding!