Upvoting rewards are given for upvotes on these accounts, too. At present, two of these accounts are posting each day in addition to the normal @steembasicincome update (for a total of three potential updates to upvote). It might be easier to earn curation from upvotes on these accounts than from upvotes on the main account.

If you often forget to curate and find that your backup system (vote markets?) regularly kicks in and sends you payments, then it could benefit you more to upvote these accounts too.

Alternatively, a more sophisticated strategy would be to setup a backup voter that lists these accounts, but with a higher VP minimum than your normal auto-voter. Then you could automatically upvote with any excess VP before selling through vote markets.