TS can HTF at anytime!!! That has been proven to me several times!!!
That's why I take the entire bundle. If I am going farther than 25 miles from home (a day's walk), then I want my BoB, including weps/ammo with me.
I also prefer to carry the maximum amount of ammo that I can comfortably carry. With my home BoB which has 2 ammo pouches on the Combat Harness, that's 80 rounds of .270cal in 8 10rd bandelero's (plastic), or about 160 rounds of .357mag/.38cal, or about 1000 rounds of .22cal.
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QMC, USCG (Ret)
The best luck is what you make yourself!