The help you offer should match the promise you made about how long you can stay.

Offering more than your promise can hold sets up a small betrayal. Help that only works if it continues, a routine somebody starts depending on, a role you fill for a while, each leaves a hole shaped like you when your time runs out. The generosity was real. The mismatch between what you began and how long you could stay is what hurts.

Say at the start how long you can do this, and choose help that can end on that date. Prefer a one time repair over a standing commitment when your time is short. As the end nears, help arrange what comes next rather than letting it stop.