It.
it depends on what what the sentence is about but somethimes yes
The verb in the sentence is: changed
space expands forever, it has no end.
He continued to dilate on the subject for what seems forever. or Darkness and light will cause your eyes to dilate.
this sentence is going to be continueing forever until i decide to end it.
No, the market would not continue to expand forever; it would stop growing when the market expands to its limits, and it runs out of unused resources.
I will keep my favorite toy forever
The subject of the sentence is "you"
A subject in a sentence is who, what, or where the sentence is about.
The painting sold
The subject is who or what the sentence is about.
No it is not a sentence. You might try: I will cherish you forever.