Do 25,000 a month so that you have 4 months of backlinks coming in.
Don't ping the blogs at all. Let google crawl.
BTW: I've blasted a site with 10,000 links (Money Site) and I just didn't ping any of the links, google is finding 30-60 a day. So don't worry about it.
And remember, if the site is making you money, then worry about deindexing. If it's making you nothing, then you really have nothing to lose and everything to gain.