I prefer the second one as it’s a bit shorter, still, longer than 70 chars, but I won’t care this time.
I usually try to stay below 80 characters as that still gives enough space on Twitter to include a Twitter handle and people can still do a “traditional” retweet.
Sorry, I hadn’t seen your Day 3 assignment – looks like you published it while I was typing my comments to your Day 2 assignment.
I like your fourth title – “without sucking away your time” is something everyone can identify with and it’s very sensory :). The downside is that “social media success” is not very specific, but I don’t think it matter in this case.
The problem with the first one is that it’s difficult to understand the concept of “saving weeks in a year” at a glance.
Enchant readers. Woo customers. Win business.