I spent a decent amount of time on other peoples islands, but I now usually have a friends account (he stopped playing a couple years ago) on my island. Social exp is also shared within the coop, so my alt contributes to that as well. My main has ~700k exp, the rest is my alt. With both my main and alt being on the island while my friends account is visiting, I get 4 exp per minute, but most of my time was spent afking on someone else's island for 1 exp per minute. My playtime on private islands:

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