Rechargeable batteries are getting better, but at the same time, more affordable by the year. Good rechargeable batteries can  hold a charge for months and cost less than a nickel per charge over their entire life. 

Keep in mind that rechargeable batteries from brands  Energizer, Eneloop, Duracell, or Amazon Basics, are of same quality.

So just buy whatever brand / model is available at a great price. If there is some promotion going on, stock up.

Just make sure you are using the right charger to charge the batteries, and never overcharge your rechrgeable batteries.

The best rechargeable AAA batteries: AmazonBasics AAA Rechargeables