Amazon just announced a new Amazon Prime membership option where you can sign up month-to-month. While this is a tad more expensive per month than getting a yearly membership, if you only think you might use it a few months of the year (i.e., holiday time period), then this is a great option! The monthly option is $10.99/month, or if you just want Prime Video it is $8.99/month (unlimited movies and TV shows are included in the $10.99/month option).
Currently, a an Amazon Prime yearly subscription costs $99, which nets out to $8.25/month. That means if you Amazon Prime 9+ months of the year, you are better of with the yearly subscription. If you find yourself using it less, then the monthly option is the way to go. I personally use Amazon Prime on a weekly daily basis, so a monthly option wouldn’t benefit me, but I know many people would love to have this type of subscription.
Remember, you can always test out Amazon Prime for free with a 30-day trial. I suggest doing this prior to committing to any subscription (monthly or yearly) as you might as well get one month free!