I have four aged 12, 10, 7, and 4. It was much more tiring when they were babies/younger but as their independence grows so does my free time. DH works full time, I'm a student and a carer for two of our DC who have additional needs and need someone basically "on call" 24/7 as well as all the other ins and outs of caring for a disabled child.
I get on with it and do it because it's my normal. I know other people look and think four kids must be exhausting, expensive, noisy, hard work, etc and if they were to step in and do it for me then they probably would find it to be that way but for me it's just how it is, I'm used to it and we have a system that works for us. Remember when you very first had a baby and it took ages to get organised, get dressed, and get out the door because you were still learning all of the steps? But then it got faster as you learned what was and wasn't needed and muscle memory took over for a lot of the smaller tasks? That's what it's like when you're settled into your parenting groove of caring for four kids, I can knock up four lunches in ten minutes and if I had to I can have everyone fed, washed, dressed, organised, and out of the door within thirty minutes of starting.
The biggest adjustment for me was going from 1 DC to 2 DC, I found it more of a shock than going from zero to one as I had to learn to balance both of their needs. Third DC slotted straight in and was so easy despite being quite a difficult baby because I knew from experience that you just have to ride out the difficult phases. DC4 was an absolute doddle, again despite being a difficult baby, because I felt like I knew what I was doing and that confidence/trust that I do it carried me through.
Supportive DH is definitely key, as is a big washing machine and a big tumble dryer- both are 10kg drum and I run a minimum of one wash a day. Organisation is important too. I have lots of storage for the toys, books, and games. They each have a storage drawer downstairs (Kallax in the dining room) and the rest of their stuff is stored in their rooms. I have a cleaning schedule where some jobs are done daily (laundry, hoovering, dishes, bathroom, etc) and everything else has a set day (e.g., Monday - change/wash bedding, Tuesday - windows, Wednesday - garden, etc). The DC are responsible for making their beds and tidying their own rooms, I'll help if they ask but I won't do it for them. Being adaptable and not worrying about the small stuff makes things less stressful.
They all have clubs they do and they get time apart to do their own thing as well as time together, we also make sure everyone gets one to one time each day with longer periods of one to one time as and when wanted/needed (for example, I took DC2 out for the day last weekend and tonight DH is taking DC3 out to look for Pokemom).
Clothing and shoes are our biggest expenses although I do keep some clothing to hand down as I have two girls and two boys, they get new things alongside the hand-me-downs and I only keep back things that are in really good condition still. Shoes can cost up upwards of £400 at a time, come August when we're doing back to school shopping and we get school shoes x4, trainers for PE x4, wellies x4, plus a pair of football boots for eldest DC I'll easily spend close to £500 - more if they've outgrown their normal shoes too. We get a holiday every year, not abroad as I don't know how our autistic DC would handle the flight, but a week in the UK plus 3-4 weekends away spaced across the rest of the year. They get to go on all school trips and residential too, they certainly don't miss out due to being from a larger family. There are no grammar schools here so 11plus and tutoring isn't a consideration, if any of them were behind d in school and we thought they needed a tutor for a particular subject then we'd pay for it. I don't ask the older ones to help look after the younger ones as I don't think it's fair, if they have friends round then I keep the others away so they get time with their friend(s), and everyone in the house has a private/quiet space they can go to if they need to.
There are days where I can be frustrating and stressful, like all children they have their difficult phases and their falling-outs, it can be tiring if one or more of them is unwell and if a sickbug gets into the house you can guarantee it'll make its way through all four of them. Homeschooling and lockdown wasn't too bad for us as they had each other, our garden is massive, and we live semi-rural so lots of walks and trails as well as the beach within a few minutes walk.