In Jain practice, garam paani / boiled water is generally best used soon after it is made, while it is still fresh and clean.

• For strict observance, it is usually kept and used only on the same day.
• If it is meant for sadharan use, many people prefer to use it within a few hours after boiling.
• Once it becomes stale, cold for long, or contaminated, it should not be used according to strict Jain care for water.

If you want a simple rule: Boil fresh water and use it as early as possible, preferably the same day.

In Jain Dharma, the main focus is careful use of water with minimum harm to जीवों.