What's the best way to store rice long-term?
If you are only using it three times a month then this 25lbs bag may last a very long time indeed.

The problem is that even white rice can eventually develop off flavors when exposed to light and air. Additionally- even if pests don't have access to the rice, it is not unlikely that the rice has some eggs on it that can hatch and spoil the whole bag.

The solutions to these problems all make it difficult to use the rice in the short term. For long-term food storage dry foods are typically sealed in either #10 cans or mylar bags. An oxygen absorbing packet is also included. This will prevent spoilage and pest growth. Mylar bags are less expensive and you can open one bag at a time for short term use.

Alternatively- if you can freeze the rice to ensure there are no pests then the rice can be stored, sealed, in a cool, dry place as others have described.

Given how cheap rice is- it might be acceptable to you to just take your chances and replace it if it spoils after some months.