Don't know if it works for other fuel sources, but In my specific instance I started smelting clay into bricks using lava buckets and four seperate furnaces, and when it was around halfway done I went to the nether and came back. The timer to show how long until the fuel ran out completely refreshed to full.
UPDATE: Seems to be just a visual glitch, as the timer showed as full up until the fuel ran out.
Is this still a concern in the current Minecraft version? If so, please update the affected versions in order to best aid Mojang ensuring bugs are still valid in the latest releases/pre-releases. If this has been done, we can reopen the issue.
Keep in mind that the "Resolved"-Status on this ticket just means "Answered", and that we are waiting for further information on whether this issue still exists or not. We will reopen it as soon as the requested information has been delivered.