How do I make parts have a lifespan?

From what I understand, do you want to make blocks spawn and wait a seconds then remove

If so, I have the solution and how you use it:

Wiki page: Roblox Wiki Page - Debris

You can use Debris.

Example:

game:GetService("Debris"):AddItem(script.Parent,3) -- Remove script.Parent in 3 seconds.

Or you can use delay:

delay(3, function()
    script.Parent:Destroy()
end)

Or wait:

wait(3)
script.Parent:Destroy()

The debris in my opinion is the most efficient.

For you script you can use this:

local Part = script.Parent -- Find part to remove
local DelayTime = 5

game:GetService("Debris"):AddItem(Part,DelayTime)

OR

local Part = script.Parent -- Find part to remove
local DelayTime = 5

delay(DelayTime, function()
    Part:Destroy()
end)

OR

local Part = script.Parent -- Find part to remove
local DelayTime = 5

wait(DelayTime)
Part:Destroy()

The best is the Debris.

Any errors? tell-me on comments.

Hope it helped!