Honestly I've not really been playing
Restaurant City much but I still visit it from time to time. Even though I'm not that active anymore I still want to progress in the game. That means I still want to level up and earn money.
So this is what I do, I raise my workers health level to 100 (if you have money just let them eat sandwiches, if not let them rest for awhile), assign them their tasks(chef, waiters and janitors). If everybody is up and running, just block the door so that no customers will enter.
Save your game then get out of Restaurant City. When you return (even after days), all your workers will be tired but you will still get some income. Previously you only get a maximum of 2000 but nowadays I'm getting 4000+ and sometimes 5000, and now you also get Gourmet Points (I think around 6,000+ GP). Which means even if your browser is not open you will be able to level up(this was not allowed previously).
Another plus by putting a blockade on your door, your approval rating remains the same. So if you have 50 "thumbs up" sign, it remains 50 when you go back. Unlike if you allow customers in, and if you were not able to go back sooner, your approval rating can go back to zero (0).
Still another plus is that when you open your Restaurant again there will be a lot of trash, so you could generally just pick it up and be able to get your "Trash" award.
Hey add me by the way in
Restaurant City here, I often have my ingredients unlock so feel free to trade with me.