How long will grease (from bacon or roast) keep in the fridge

Most cured products last 7-10 days in the fridge although you most likely will see a quality drop off before then at around day three or four. You can also freeze the bacon for up to two months and thaw for use to extend the shelf life.

Food tends to become unpleasant before it becomes actually dangerous. I would try to eat things within 3 days of making them, though that's just my personal guideline and isn't based on any scientific data. If you aren't going to eat it that quickly, freezing it after it's been cooked and thawing it the day you want to eat it is probably a better idea.