Despite both questions being tagged discussion, I am pretty confident that the difference in votes in the second question is mostly due to:
- The arguments given
- The humour used in the bounty and the edit
Also, there have been discussions on feature-requests with hundreds of upvotes yet, which still haven't been status-completed. Recently resparked: discussion on disabling the language filter. Follow the chain of related questions and you will see what I mean.
Conversely, there have been topics which were generally not received well, but have the status-completed tag: https://meta.stackexchange.com/questions/tagged/status-completed?page=436&sort=votes&pagesize=15.
All this to say, up/downvotes probably do not matter too much when it comes to decisions about what gets implemented. It also goes to show that some discussions can drag on forever, spanning multiple questions, while others are concluded on a very short notice. So concerning your first question:
What is a realistic timeframe to reach consensus or review a topic?
About 6 to 8 weeks!