I think the closer in age they are, the better. So now would be best! No pressure though. haha.
We got Punks when he was 4, when Stiggy was 1 and a half. They're not that close in age, but they do wrestle everyday.
And Punks joining the family didn't disturb the routine much. I actually feel less guilty leaving them at home alone because they keep each other company. And it's less tiring because we used to always had to keep Stiggy occupied when he was an only bully. The only difference is the the vetting costs. Punks came with loose knees, so we look after them regularly with supplements and laser therapy. And when they both need to be seen by the dog-tor, that's another pretty penny! But they're oh so worth it! No regret. Nuh-uh!