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Promoting for 2-5 days is more effective if you're posting content people are likely to vote on. Otherwise, boosting is better.

You might also want to check out @dustsweeper, you send it a bit of Hive and it returns it to you as votes, ensuring none of your posts are below the payout threshold.

Only comments tho. Not posts

Well it depends. If you have a business or airdrop to share. U can use promote.