When Steem turns around your stake should be more than sufficient. There is no reason to add unless you really want to.

I still invest in Steempower mainly because of the RC credits which I think will be very valuable when Steem grows and also because STEEM will become the main trading pair vs SMT's (Steem-Engine already has shown the potential of these tokens).

Currently, it is nice to have more Steempower for curation and the ROI it provides while I wait for the network to grow. I think #newsteem will help a lot in that regard.

The main focus of my blog has always revolved around Steem. When that is no longer wanted (for example: on youtube, nobody talks about how great youtube is) I will stop blogging and make my SP work for me in other ways.

Ultimately, I want to use my stake mainly to lease to or invest in projects/applications/communities for a decent return on investment.

I think the only person that can convince you that this isn't monopoly money is yourself. If you want to invest you can always do it later. There is no rush.