All those different types of fuels are being used simultaneously. BP projects a global R/P ratio of:

40.6 years for oil.
65.1 years for natural gas.
155 years for coal.

According to BP, the estimate for oil includes oil sands "under development" as well as gas condensate, natural gas liquids, and crude oil.

Proved reserves are taken to be those quantities which geological and engineering information indicates with reasonable certainty can be recovered in the future from known reserves under existing economic and operating conditions.

That's existing conditions. But consumption is growing. If a declining balance were used instead, together with a linear growth in consumption, you would find that oil would run out sometime between 2032 - 2045. If we then start using coal liquefaction for transportation fuel and start consuming coal at the same rate as oil, it'll be depleted in 50 years instead of 155.

Depends on alot of things of course. When the USSR broke up their collective oil consumption dropped by 50% and stayed low for several years. And just because some country has alot of a particular resource doesn't mean they will export it to us when we run out. For example, China may decide to block exports of coal to protect their own energy supply. If this happens then the global R/P ratio is meaningless, and the regional R/P ratio is most important. For us in the western hemisphere that's bad news. Hell, the global R/P ratio was bad news!

I'm flippant now, but in 30 years when I'm supposed to retire and the world is running out of oil and wars are being fought and the world is in economic depression, I'll be looking for a way out, just like everyone else. I think what we need today is a little collective decision-making. Everyone, everywhere, just decides to do things the right way, to preserve our future, to prevent resource depletion. Probably wishful thinking though. And I'm in no position to head-up such a "hive mind" type of scenario.