Someone I work with shared with me her “2 hour policy.”
If she goes out to see friends for dinner … 2 hours, and she’s had enough. 
If she’s asked to look after her grandchild, of course she says yes … for 2 hours only. 
And … yes, you can guess. Whatever she’s doing, socially, the 2 hour rule applies. 
Her reason? She says she knows her limits … and living her life this way allows others to get the best out of her for 2 hours. 
I’m still pondering on the idea, but in the meantime … I do rather like the idea of quality over quantity. 
What’s your take on it? Is 2 hours enough for you?