Depends on how you define "consensus" in meta.
After something has been posted in meta for a while, it's reasonable to presume anyone interested has had the chance to weigh in as much as they wish. If a proposal receives no discussion from other users, and isn't debated in the main chat room, one can only presume that other users have no opinion on the issue, or just don't care.
Votes, up for agree and down for disagree, remains the only useful metric. If the votes in both directions are nearly split, then the lack of consensus makes sense. On the other hand, if there are only a few votes, yet they agree, in the main, the presumption is that of the users who care about it, the opinion is "good idea," and moving ahead with proposed action(s), especially ones that are trivial to reverse, is likely the best course to follow.
For most issues on a site this size, and in beta besides, one cycle of the timezones seems like it should be enough time for interested users to express whatever opinions they might have on the subject. As the site's user base grows, especially as more users get involved in the meta of the site, a longer period may become expedient.