Thanks Chris for support and advice.

Yes, will definitely boost less the next post. As I have some Steem to power up, I think it's more advantageous to use them for promotion first. Indeed post payouts will transform themselves in SP. After a few weeks, the result will be an increase of 15 - 25% more SP from the starting investment.

I think promotion by botting is a fantastic tool for newbies / minnows / plankton as they can level up. Other option is to continue writing 70+ posts with 0.000 STEEM payouts like I did. All this with no comments at all.