At the earliest — by the time fuel oil season arrives, the inventories have been purchased and stashed in the distribution system. I can tell you though, the winter of 2013-2014 was nasty cold here, and the cost of four months of heating (with the thermostat turned down to 60 almost the whole time) would have paid for a new furnace, no problem. Probably would have paid for a chunk of the natural gas heating costs for that year as well. Out here in the country natural gas is on a sudden rise. Propane, the other white meat, is a byproduct of crude oil refining, so its price more or less followed crude up and down (and mostly up).
I think it will stay at 40 - 60 for a year at least, unless Putin is expanding his war.