I moved house in August, and have had a 26 km commute so roughly similar. Mine's got 50 metres drop on the way to work, so mostly flat.
In my experience, you're in the distance where comfort becomes more important. Anyone can smash out a short commute every day, but these longer ones cumulatively build up on you.
Clothes So expect to spend money on contact points and clothing - eg I've bought 4 pairs of armwarmers that all felt good initially but have had issues on the long ride. Your cheap pants are probably fine for normal commutes, but try different sorts/brands. I've had good luck with some cheap boxer-style padded shorts for under normal pants. But I also own one pair of bib shorts and that's a nice change. Do be aware elastic sags with age, so what was a good fit might have loosened off to give some rub now. (check for existing question about good-fit shorts)
Cumulative Check with your employer and see if there's a work from home policy that you can resort to, if things are getting just a bit too much for you. I use this about once a month when its really heavy rain on the way in.
Variety Do make an effort to mix up your routes. I have limited options because there's only so-many roads, but try and go different ways. If you have a bit of extra time, then try going right out of your way.
I also ride a couple of very different bikes. A commute on the road bike is very different to the recumbent.
Safety I have illegal quantities of lights on my bikes, because 20% of my commute is in pitch darkness with no streetlights and a 80km/h speed limit and minimal road shoulders. Its terrifying when you're not sure if the approaching car has seen you or not.
Food/drink I have a gel sitting in my toolkit in case I feel a bit underfuelled. Have needed it twice. I tend to not drink on the commute though because its not in the heat of the day. However I know where some public drinking fountains are on the way.
Preparation you're going to get punctures, so make sure your bike has all the tools and spares on it. I carry a spare tube and stickers in case of additional punctures. I also carry spare disposable batteries for one front and rear light.
Ebike Its going to be easier with the ebike, but don't depend on it. Some day you might have to ride the entire commute with a flat battery. Can you do that?
If you have a second charger, consider storing it at work. They cost cents to charge, so work shouldn't have an issue, but depending on the culture you may have to ask/check for permission.
Personal Bests (PBs) I got PBs whenever there's a tailwind. But I'm now at the point where we'd have to have a 30+ km/h wind to shave a second off any of my times. The good side is that daily commuting means a fair chance of a tailwind. But an equal chance of a headwind on the way home. There's no such thing as "Personal Worst (PW)"
Backup plan I have a bus route that passes within 200 metres of work and home. Never had to use it yet, but if things were dire I could jump on and let someone else drive me. These busses have bike racks for normal sized bikes, so the recumbent would have to be pushed home. I wear flat shoes on the bent so that's possible, but cleats on the road bike so I carry covers in my on-bike toolkit.
You might benefit from a proper bike fit too - the time on bike could be exacerbating some minor problems. Expect to pay for this and take several hours.
Fun to be honest the fun kinda drops from cycling when you're grinding out those kind of distances. I used to do 100km+ weekend rides when my work commute was 1.5 km. Now I prefer to stay at home in the weekend.
Weather Buy good rain clothes, and check the evening forecast before you leave home. If you can, store clean/dry spare clothes at work, including shoes and underware. I keep two towels too, and switch them home periodically for a wash.
Shower If your workplace has a shower, great. If not, consider a gym membership near work just for cleaning up.
Maintenance Keep on top of it - your bike will be doing 600 miles / 900 km a month, so a normal chain may only last 3 months, or an IGH oil change will be needed every 6 months. Its up to you to not forget. I'd suggest a monthly maintenance session, perhaps more in Winter.
Strava Do use strava to record your rides. It gives you a lot of efforts on segments, and the graph shows if you're improving over time or not.
Music This one is contentious, but time can go faster if you have some music to listen to. Exactly how you listen varies, but there are good options that do not block your ears, like bone conduction headphones, or small personal speakers. I sometimes front-load and let an earworm song play on and on and on, and on and on....