Down Time at Night When the Other Child Sleeps

Packing in some evening time of peace and tranquility is now crucial because in less than three short months I will join new motherhood again where evening time and peace are mutually exclusive. It's either one or the other,  Evening time will be filled with the pitter patter of my four-year old's footsteps as she finds yet another reason to get out of bed, coupled with the sure-to-be frequent wakings and feedings of the newborn. I have to savor the peaceful time in the evening I get now, after which point my daughter is finally asleep. Once those consecutive fully-occupied nights of making sure both kids sleep come, I can kiss the alone time away. Even now here's the routine with my daughter:
Go to her room at 8PM to read books.
Lights out at 8:30PM.
A story is told.
Then she tells a story.
Then a kiss and her request to come and check on her frequently until she falls asleep.
During those promised check-ups, she gets up at least two times to go to the bathroom and to remind me that I haven't checked up on her in the last five minutes. Tonight I told her that the deal was off for the frequent checkings. I told her I would only check up on her once she was asleep. I would kiss her while she slept. Already tonight she has gotten out of bed twice to go to the bathroom. The first time was legitimate. The second time wasn't. I have to get her to do all of her bathrooming before we even go to the bed at 8PM. Yet she drinks water before bedtime, so I know that it's only a matter of time before she needs to pee. It'll be either at 9PM or at some indistinguishable hour in the middle of the night. Either way, my peace and tranquility are interrupted. I love that she's potty trained, but she adores visiting the toilet. Once she's really out, sleeping with that heavy breathing, then I truly relax. My cat joins me on the couch, purring loudly. And I read, use the computer, or watch a DVD. I crave this time and it lasts for two hours...if I'm lucky. In December, this will all change. My goal is to move my daughter's bed-time up one half hour, so that she is asleep by 8:30PM. Then I will prepare myself for whatever baby will bring me in the evenings.  My mother had six kids, and I recall we were all in bed at her command. And if too much noise was coming from the bedroom I shared with my two older sisters, the sound of the banging of the end of a broomstick could be aptly heard from our floor. We would immediately silence ourselves. My mother surely needed that evening time alone. Now I get it. Boy, do I get it!