Current twelve hours fuel cycle for steel crucibles is too short and doesn't integrate well with real life.
While some things need to have a failure rate to make things interesting, it probably shouldn't be a factor of how often a player can login at specific times especially when it comes to a critical resource (brickwalls). It makes it nearly impossible for some to produce steel and just makes you want to bot it which is in itself even worse.
Perhaps it would be worth considering increasing it to 16 hours or reduce the amount of cycles at the expense of more fuel per cycle?
Scheduling your RL around being online at least every twelve hours during the span of four days is no fun.