I do cross countries in an Archer quite a bit.... my last one was the farthest I've ever gone, from my home base near St Louis all the way to FL.
Your airplane doesn't really care if it's going 50 miles or 350, and you can get yourself into trouble just as easily 50 miles away from home. Biggest things are going to be airports you're not used to... which you've probably done before on your short hops and airspace you're not familiar with. Study your route... look for big towers, MOAs, restricted airspace, high terrain(hills/mountains), and any major airports/other airspace.
Foreflight is a great app, I only have the gen1 stratus and haven't tried synthetic vision. I use foreflight as a smart sectional and tuck it away in the map pocket or leave it in my lap, checking it every few minutes. Turning the ipad screen off when you don't really need it makes the batteries go a lot further. I usually carry a USB power bank and wall charger... as well as a cigarette lighter charger. Normally I don't need to recharge with the power off while not looking at the ipad method.... I navigate primarily by a panel mount GPS and only reference the ipad as I would a map YMMV.
Use flight following. If you're not used to doing this, start. They'll warn you about and help vector you around hazards along your route, warn you about nearby traffic, and give you generally helpful information. Also, if something does go wrong you're already on frequency with someone who may be able to help. Some controllers are more helpful/friendly than others... sometimes there's very little going on and they're quite bored and others you'll be watching minutes go by waiting for people to stop talking on the radio so you can check in. If you're not so good on the radio, practice just like you did when you learned how to land or anything else in the airplane. A notepad and pen helps if you're having trouble remembering the frequencies/squawk codes they give. Most of the time they don't mind repeating the information if you missed it the first time.
I personally limit legs of my trip to about 3hrs. If I find myself facing a trip where I can make it in 3.5, I might fudge that but I find around 3hrs of hand flying is where the body and bladder like to take a break. Also don't leave an airport without filling the gas tank if you can avoid it.
Speaking of body and bladder- bring a bottle of water and a bag of something to snack on. I like beef jerky... I don't always eat it but I don't go on a long trip without it. Sip your water to keep your throat from getting dry.