If I could only pay for 7 months at a time instead of a year it would help

Why would I have to pay for a full year?

Well technically you don’t have to. There is nothing to stop you using the Avast Essentials Free version.

Most software subscriptions are annual renewal.
The only exception I can think of is some VPN services can be on a monthly basis, which ultimately works out more expensive than an Annual subscription.

Whilst I have never used the Avast One product (Essential or Premium), I have been using Avast Free for almost 20 years now.
However there is a little more included in Avast One Essential than Avast Free, however Avast One Essential it doesn’t have the same level of configuration as Avast Free.