You use the mappers to show where to go at any one time.
Wormhole lifetimes vary by size and category. Some will live for 18hrs I think.
The thing to remember is that the statics are linked to a class of space, not a particular destination. In your earlier example, hole C1-1 has an NS static - that is, that system (call it J111111) will always have a wormhole leading to null. When you visited it popped up in Omist. However, after that hole closes (either by timing out, or being “rolled” - each wormhole has a certain amount of mass that it can pass through before it closes), the next one to open in J111111 may lead to Delve.
The other hole you encountered in J111111 was what’s known as a wandering - that is a wormhole that randomly pops up and could lead to a range of other space types, depending on the system class, constellation and so on. In your first trip, it found C1-2, or J222222. However, as this was a wandering hole the chances of finding those two wormholes connected in your next visit to either system is pretty low!
J222222 had, for arguments sake, a HS static. So, there will always be an exit to HS, but this could be anywhere within empire space.
With that all covered, you can hopefully see that by using a mapper, once you’ve found the route from Omist to highsec, anyone sharing your mapper can see the route and make that journey while those wormholes are alive. You’ve gotta move quickly, but if you get a nice Jita connection you can save yourself a whole lot of trouble just shimmying on through.
As others have said, once you’ve got even half a dozen halfway decent scanners out you can find a lot of connections pretty damn quickly. And once you get some of the common connection types in your head, you kind of know where to head to find whatever you’re looking for.
Anoik.is is a great resource if you wanna find out about wormhole systems, has a full list of every wormhole system and its statics / wanderings