Those of you who still have little ones of your own have a tougher job than dcproviders like me. But I went through it too, way back when. The only difference was my dh worked till 4 or 5 and figured his work day was done so he didn't lift a finger once he got home. I needed to have supper on the table, see all the dcks off, clean up the house, bathe our own kids, read them stories and tuck them in. They'd run out to his recliner(heaven forbid if it interrupted anything but a commercial) and hug him goodnight. Resent much? Yeh I did. Anyways, I honestly cannot remember any ME time back then. Weekends were my time, when the yard sales hit, but I still took my kids with me. So I was never alone. I literally cried in private because I yearned for just 10 minutes of solitude.
I would reenforce quiet time, for you, if for nobody else. Even on weekends. Your 7 yo can read books or color, play blocks or something while your younger ones nap. Make it for an hour and let them know that no way are they to bother you, unless the house is on fire. As for longer blocks of time, Have no clue. I don't remember any social life without bringing the kids along. Carving out a little time here and there is better than no time.
Much luck to you!!!