(The "Help Sought in Finding Affordable Fares to Europe this spring/summer on UA" thread" is specific; this is a more generic question about finding reasonable fares. No problem if the mods feel otherwise)

I'm continuing to play russian roulette with my upcoming SFO-CDG (could be SFO-GVA-CDG-SFO) for mid-July. Hoping that UA becomes a bit less proud of its inventory and prices closer to the *A codeshares that are currently running 15%+ less than UA metal.

Question is, how often should I be checking? Do random cheap fares pop up for no good reason and quickly go away, or is there an orderly system in place that would allow me to check only a couple times a week and believe I haven't missed anything?

The thing that UA does that makes me think I need to check fairly often, despite people here saying new fares are loaded on a certain day of the week, is that, over 4 consecutive days, UA will throw different flight options at you for the same trip. For example, when searching by price, one day SFO-CDG will route through IAD, another time ORD, and then FRA. Rarely, LHR will pop up. You'll get six or seven options all featuring the same interim hub on any given day. And then it changes the next. And all at similar pricing.

Actually, that was the pattern in the past, before UA decided to feature the codeshare flights instead of their own metal. Now, it will feature Montreal one day, Houston another, Newark the next.

So that's why I'm thinking UA changes things more often than is typically assumed. But maybe UA is deliberately manipulating me because they're getting paid by someone else on a bizarre pay-per-click scheme and they've hit paydirt with me.