Correct, you can layer copies of the same spell to protect against dispelling. They don’t do anything else, that is, the is no difference between having 10 copies and having 1 copy until you get dispelled, but you can do it. There is no limit (aside from your spells per day, or at the extreme, the number of times you can successfully cast the spell before the duration of the first wears off).

This is not a sound strategy, however. You have a limited number of spells you can cast each day, and you generally want each to actually do something. Dispelling is certainly a risk worth protecting against, but it doesn’t come up constantly, so a lot of those redundant spells aren’t going to come up, making your proposal extremely wasteful.

It also isn't as good at protecting the spell effect as you might think. When dispel magic is used on a specific target, e.g. you, it attempts to dispel every spell on the target. That is by far the most common way to dispel anything. So it is not as though this approach guarantees that it will take 10 dispel magics to eliminate the effect. Forcing them to roll repeatedly does mean they are more likely to miss some, but now they are killing multiple 4th-level spells with a single casting of a 3rd-level spell.

Also, few spells are as amenable to this idea as death ward: its natural 24-hour duration means you could cast it repeatedly at the start of the day, and probably not have to again. For spells with a shorter duration, you have to cast them multiple times per day, driving up the costs, and you often won’t have time to cast multiple copies. Or you want to use Divine Metamagic (Persist) to make them last 24 hours, but that requires 6 uses of turn undead each time, limiting how many times you can do it.

Finally, there are just easier ways to protect against dispelling.

Correct, you can layer copies of the same spell to protect against dispelling. They don’t do anything else, that is, the is no difference between having 10 copies and having 1 copy until you get dispelled, but you can do it. There is no limit (aside from your spells per day, or at the extreme, the number of times you can successfully cast the spell before the duration of the first wears off).

This is not a sound strategy, however. You have a limited number of spells you can cast each day, and you generally want each to actually do something. Dispelling is certainly a risk worth protecting against, but it doesn’t come up constantly, so a lot of those redundant spells aren’t going to come up, making your proposal extremely wasteful.

It also isn't as good at protecting the spell effect as you might think. When dispel magic is used on a specific target, e.g. you, it attempts to dispel every spell on the target. That is by far the most common way to dispel anything. So it is not as though this approach guarantees that it will take 10 dispel magics to eliminate the effect. Forcing them to roll repeatedly does mean they are more likely to miss some, but now they are killing multiple 4th-level spells with a single casting of a 3rd-level spell.

Also, most spells don’t last all day, so you have to re-cast them. Often, you won’t have time to cast multiple copies. Or you want to use Divine Metamagic (Persist) to make them last 24 hours, but that requires 6 uses of turn undead each time, limiting how many times you can do it.

For spells which naturally last hours, it becomes more plausible.

But ultimately, there are just easier ways to protect against dispelling.

Correct, you can layer copies of the same spell to protect against dispelling. They don’t do anything else, that is, the is no difference between having 10 copies and having 1 copy until you get dispelled, but you can do it. There is no limit (aside from your spells per day, or at the extreme, the number of times you can successfully cast the spell before the duration of the first wears off).

This is not a sound strategy, however. You have a limited number of spells you can cast each day, and you generally want each to actually do something. Dispelling is certainly a risk worth protecting against, but it doesn’t come up constantly, so a lot of those redundant spells aren’t going to come up, making your proposal extremely wasteful.

It also isn't as good at protecting the spell effect as you might think. When dispel magic is used on a specific target, e.g. you, it attempts to dispel every spell on the target. That is by far the most common way to dispel anything. So it is not as though this approach guarantees that it will take 10 dispel magics to eliminate the effect. Forcing them to roll repeatedly does mean they are more likely to miss some, but now they are killing multiple 4th-level spells with a single casting of a 3rd-level spell.

Also, few spells are as amenable to this idea as death ward: its natural 24-hour duration means you could cast it repeatedly at the start of the day, and probably not have to again. For spells with a shorter duration, you have to cast them multiple times per day, driving up the costs, and you often won’t have time to cast multiple copies. Our you want to use Divine Metamagic (Persist) to make them last 24 hours, but that requires 6 uses of turn undead each time, limiting how many times you can do it.

Finally, there are just easier ways to protect against dispelling.

Correct, you can layer copies of the same spell to protect against dispelling. They don’t do anything else, that is, the is no difference between having 10 copies and having 1 copy until you get dispelled, but you can do it. There is no limit (aside from your spells per day, or at the extreme, the number of times you can successfully cast the spell before the duration of the first wears off).

This is not a sound strategy, however. You have a limited number of spells you can cast each day, and you generally want each to actually do something. Dispelling is certainly a risk worth protecting against, but it doesn’t come up constantly, so a lot of those redundant spells aren’t going to come up, making your proposal extremely wasteful.

It also isn't as good at protecting the spell effect as you might think. When dispel magic is used on a specific target, e.g. you, it attempts to dispel every spell on the target. That is by far the most common way to dispel anything. So it is not as though this approach guarantees that it will take 10 dispel magics to eliminate the effect. Forcing them to roll repeatedly does mean they are more likely to miss some, but now they are killing multiple 4th-level spells with a single casting of a 3rd-level spell.

Also, few spells are as amenable to this idea as death ward: its natural 24-hour duration means you could cast it repeatedly at the start of the day, and probably not have to again. For spells with a shorter duration, you have to cast them multiple times per day, driving up the costs, and you often won’t have time to cast multiple copies. Or you want to use Divine Metamagic (Persist) to make them last 24 hours, but that requires 6 uses of turn undead each time, limiting how many times you can do it.

Finally, there are just easier ways to protect against dispelling.