My team is split across several countries, I don't need to see my teammates in person on a daily basis but I like to have the chance to see them once or twice a year and also tackle specific problems, run some workshop together during hackathons and participate in a teambuilding event.
TBH I feel like it's just a little much, but not much more than a little much. In other words, I think probably two weeks (10 full days) is probably a good minimum because I do see some value in seeing the team once or twice a year in person. So somewhere between 10-20 full days is probably the sweet spot for me.
2 weeks every 6 months doesn't sound extraordinary to me. These are not vacation, these are regular work days. For an engineer I would imagine that would be what we call hackathons.
It's also usually a huge, ridiculous cost to the company. A few companies ago they spent a million or so sending us 200 employees to an island. It would have been cool if it hadn't been immediately followed by layoffs citing cash burn being too high.
Recently many companies are cutting back on the fun part of the offsites and holding them onsite or nearby the office to reduce costs. I've been to a few "on-site offsites" that were just in a different building than we normally sit in with light refreshments served afterwards. I imagine since Dropbox doesn't have much of an office presence anymore they probably still do destination offsites and fly people in.
Source: this is just something you learn working in tech in the bay area
I'm pretty sure Dropbox flies people in for these.