Thanks Adrienne!
I think re the visibility you are right, leaving well considered and relevant comments on other peoples post are really the way to go. I do it often and in fact in commenting I find the seeds for new posts on my own. (some comments of mine get out of hand and really should be posts)

re the sustainability:
As long as I don't have to put in money extra, I can keep on going
indefinitely.
Say I randowhale the post for initial visibility.
If it earns me say 12 SBD total through upvotes, - 2 SBd for the Randowhale
10 SBD left:
I'd be more than happy all day long to split up the remainder with constructive commenters.
Because all the while my SP is growing and will build my profile.
So my bet is that this way I will still make out better than keeping the SBD for myself... if it attracts attention enough of course. Can't lose really