As with many things that involve the word spam, like spam is not a good idea. Any credits you would gain from like-spamming are forfeit by the act of like-spamming, and it only serves to clutter up the forum activity feed. It serves no benefit to you or the community, and on behalf of everyone I would like to ask you never to do it. You can, obviously, like exceptional or funny posts from time to time. Nothing wrong with that, and it can serve other useful functions as well. Just no spamming of the feature.