Yes, , the secret is often in the amounts, or in the way foods are processed (canned for example.)
I think you are right; if we eat small amounts of trigger foods, just maybe once or twice we can be OK. But I think I overdid it, carrying on for 4 days there!
Even though I read that small amounts of garden peas and peanuts are low Fodmap!
Maybe it's accumulative, and we should leave a break in between testing any possible trigger foods in small amounts. Low Fodmap or not, those foods always made me "go" (bathroom) even well before I had any gut problems.
I am still to a great extent on low Fodmap foods. Sometimes I try to extend that slightly, by trying just a little more than 2" of celery....maybe 4", and testing a few mange-tout peas, trying a small amount first (maybe 3), see how I go, then add one each time, and that kind of thing.
I try with other foods too, apart from the above. Those are just examples.
Now from the very beginning I never had any problem at all with gluten, so generally didn't give that up, except for a 6 week period when I only ate gluten free, to see if that helped, and it didn't. Likewise, I never had any problem with small amounts of chocolate (luckily!) or even honey -ever -which is notoriously high Fodmap!
In fact I got a lot of help last winter by eating top grade, medical quality Manuka honey. But it was too expensive to continue. I spent hundreds on it in six months and had to stop.
So yes, I am coming from a safe food list which is low Fodmap (apart from the above which never bothered me), and trying to extend my food repertoire inch by inch.
I guess I learned from this that 4 days on those foods (or even 3?) is too much, and my cut-off point appeared to be two days.
But the downside (apart from flaring sometimes) is wasting food. I hate food wastage, and never ever did that in my life. Because I live alone it's harder. If I try a food, eat tiny amounts, and find after a few days they don't suit me, it means I can't try those foods again at least until my next "better period".
The problem is, most are fresh foods, and they won't wait that long. I end up wasting food as there's nobody else to eat it. Sad.
Buying frozen veggies instead seems to be more sensible.