Part 2 of 2 of my reunion head-canon.
It takes around 4 years for them to get back together. Lots of venom and awkward stink eye between.
And heroin. Lots of heroin to try and beat Sherlock's head into submission.
Partying in Mycroft's extra bedroom like a weenie listening to Gotye or something, goth makeup slowly developing on his face.
Someone's going to reeeeehaaab.