Roomba 630 - replace battery time?

I have the following item for 3 years now and use it 1-2x a week and leave it on charge station at all other times.

The past few months, I've noticed it only goes for about half an hour or so now, and I never really paid attention until recently, and looking at the reviews on amazon here: https://www.amazon.com/product-reviews/B008LX6JWG/ref=cm_cr_dp_srch?filterByKeyword=hours&search-alias=community-reviews

it seems like it should be lasting 1.5 or more hours.

Can someone point me in the right direction in terms of replacing the battery, or resetting (?) or whatever I may need to do to help with my problem? Thank you!