I had similar question as OP - if i could experiment with PBNs on tier1 and suppose got punished or deindexed will it hurt the money site. Guess the answer is yes after reading the replies in this thread.
Loaded 5$ to test it out and the upvotes started coming within minutes!.
Post is still there after a day and upvotes aren't removed.
Very good service. I'll use it more and give another review if anything changes but so far so good :D
Google holds rankings for a few days/weeks when it isn't sure that your site gained links legitimately or gaming it.
Basically any site that isn't already in the top sites of the world will experience this, your legitimate SEO or following google's guidelines(bullshit) isn't going to change...