This should be solvable by enabling users to set different timeframes for each of their categories targets (rather than for all targets - as Hugo’s screenshot suggests). That is something that has already been built into the feature, judging by the settings that you see when you retrieve targets via the API -
Having said that, some bills might need to be paid more regularly & as a result, more granular categories will be needed when they’re reviewed in a couple of months.
Edit to strikeout text was made after Ben’s later comment