The end is when COVID is either endemic in your country, or is no longer able to spread exponentially even without any non-permanent large-scale interventions.

The end is when COVID is either endemic in your country, or is no longer able to spread exponentially even without any non-permanent large-scale interventions. Sweden can't "throw in the towel" and go back to before 2020 -- the people who have died have already died (and notably, more than half of the COVID-19 deaths so far in Sweden happened before May 1, and about 90% before mid June). Implementing lockdown measures now won't bring those people back to life, and since the number of cases is low and continuing to decrease now, also would have very little benefit otherwise. Unless you're referring to stopping lockdown measures as "throwing in the towel and admitting you fucked up", in which case the answer is "definitely not before there's some plausible story you can tell about why it's fine to do that now but wasn't before". And any country that hasn't had widespread community spread like Sweden is likely to see the same sort of spread Sweden saw early on if they implement the same measures Sweden did.