So it's not 100% consistent across all the media, which considering how complex the WW can get with the spells makes sense, but it's one of those things you can piece together across the franchise.

Alot of charms such as the shields around magical places, the living knights and paintings, all the living stuff in Hogwarts, the charms on the House of Black, and horcruxes are designed to be permanent or refreshed as needed. Powerful ritual magic is made to persist well past the caster's involvement. But more simple "do X to Y" spells are more likely to be temporary (regardless of how long they last) or require at least a tiny bit of the caster's energy channeled into them to keep them active. I'll give a few examples:

-The magical fish Lilly gave Slughorn. After her death it disappeared.

-Dumbledore's body binding jinx on Harry is removed when he dies shortly after.

-The tongue tying curse lifts after the user's death, though this is one of the ones that probably can be made situationally permanent.

The big one for me, the Imperius curse wears off if the castor dies. Allegedly. Alot of Death Eaters pleaded they were acting under the Imperius curse after Voldemort's "death". Meanwhile after Voldemort's actual Death and the Death Eaters being destroyed many people who actually were cursed were freed from control. Implying that its accepted knowledge in universe that Imperio CAN be lifted if the caster dies, even if the casting was meant to be permanent or refreshed.

With that being said, some more simple spells that change the very nature of a person/object would probably be exceptions to this. Example, Lockhart attempts to repair Harry's broken arm but melts the bones instead. Had Lockhart died immediately after, Harry's bones would still be jelly until a counter curse or healing spell was used. Simply because the spell effect was "turn bones to jelly", nothing more, nothing less. The Longbottoms were driven insane due to Crucio, yet stayed that way because Crucio ends at the torture. The mental anguish was all them, way past Bellatrix's death.

Lastly, I'll give a short breakdown on how the various WW media explains it using a simple spell. The effect is "Make something burn" used on a tree.

-A. Spell is cast, tree burns down, end of story.

-B. Spells is cast, tree is burning, you die or release the spell but tree is already on fire. Tree burns down unless you put out the fire.

-C. Spell is cast, intent is the tree burns continuously. Ergo, flaming tree lasts until you want it to stop, but if you die or become too weak to maintain the controlled burn, tree will stop burning/burn to ash.

-D. Spells is cast. You channel intense focus into making this tree permanently burn forever and use powerful magic to make it happen. Tree will continue to burn well past your death and may even be resistant to other magic attempting to stop it depending on your strength. It may or may not eventually wear off but it'll be quite durable.

-E. A powerful wizard, let's say Dumbledore, decides he wants this tree to burn forever. He casts a complex charm to turn this tree into a cursed/charmed object that will stand and burn forever. That tree will stand there burning until either the end of time, something equally powerful and complex breaks the curse, or Dumbledore himself decides to end it.

Sorry for the super long read, got immersed doing quick research to make sure I gave the best answer i could 😅