Structure the game differently.
Give time to your time, make regular work too rewarding to interact with the game itself, indicate the plot about events at your players rather than the things your players are looking for, or a number of other things.
Do not make mistakes, If you allow this type of game to lead to success without inconvenience, you will never be able to convince your players that this strategy is not effective. Because if it can succeed without any inconvenience, it's probably a dominant strategy on any other possibility.
If the game is set up so that players can choose to burn for three months and the plot will wait for them, there is no inconvenience to allocate unlimited stopping times to accumulate resources. Players do not spend their time or attention on mundane and boring tasks, but they get the same rewards as they did.
They can also spend indefinite shutdown times in a particular forest, reaching an infinite level of progress in your system and thus having endless options for resolving conflicts at a time that suits them. the best. Think of it as follows: What are the real life factors that prevent a person from working for three months and then become an unstoppable hero of action?
The most direct solution is to prohibit or counteract, formally or informally, strategies that allow ordinary tasks to achieve goals in play. You can do this with a specific player-MJ agreement that states that they will not behave. in this way or, at the other extreme, could make time play a crucial role in the game, so that spending enough time on mundane activities to earn money and make money trivial challenges too. means that the opportunity to participate in these challenges has passed.
If their job is to steal an artifact, maybe it's only in town for two weeks as part of a traveling exhibit in a museum. players basically can not wait to try to get the artifact.
If the elements of the plot are things that can happen to the players, whatever they do, you can refuse to allow them to spend three months doing ordinary work without meeting the content you have planned.
Perhaps the useful equipment is it so expensive that sweeping taverns soils never generate enough revenue to buy it, and playing with the content you have planned is the only way to get that kind of money.
As a game master, you have unlimited options to apply the items you want to apply. You do not need to, and should not expect to, simply accept what any player suggests at any time. As in NautArch's answer, a 0 session is a great way to get everyone on the same page. But even without such an agreement, you, as GM, have much more control over the feasibility of these ordinary gaming styles than you think.
Use this power to bring the game to your players!