Assuming you're on google.com/flights, I'm fairly sure that using a VPN, changing your IP, flushing your cookies... none of that should change the availability and pricing you see on Flights.

And no, don't bother trying to time your bookings. It's kinda like the stock market; trying to beat the market, er, optimize your flights purchase time is likely to lead to sorrow and regret. From the research our Google Flights team did recently, we found that if you wait a week, on average you're gonna pay more for the same flight.

And no, we didn't see any universal discount on Tuesdays, either ;)

I only have one VPN, GoldenFrog's VyprVPN service. Sorry, I didn't intend to suggest that I was running multiple VPNs.

I haven't experimented extensively with things, but usually setting my exit server to a random country on the other side of the planet (e.g. Malaysia) has yielded consistently good results.

And yes, I do tend to book on Tuesdays.

I would be interested on this as well!