At what interval should I refill propane tank

[GypsyCliff]

I am doing rather well on propane usage, but coming up on an issue. When should I draw the line, and go fill it up, again? (For whatever reason, propane dealers will not deliver)

I have never ran it dry, so I don't know what the meter reads, at that point.

I have the control panel display, inside, and a meter on the tank in the propane bay. The meter is a round dial, with hash marks around the circumference. It is marked 1/4 - 1/2 - 3/4 at appropriate intervals.

I don't have the guts to run it down too close to 0, as I am allergic to cold!

Am I safe to go down to 1/4? Lower than that?

Thank you,

Cliff