I consider easements only valid when in use, or 5 years. That is once you build the "thing" you get to keep the easement, but if you stop using that pipe/cable/... you get 5 years to clean it up. If you are planning on building, you get 5 years to complete it, otherwise you have to start over getting another easement.
I was recently involved in a civil suit where an 50+ year old easement was brought up. I’m glad you only consider the easement valid for 5 years or when in use, but the courts disagree.
Maybe. Many are forever. If the restriction is a via HOA there is generally a process to modify the HOA agreement. However there are other restrictions and some don't make provisions.
Nothing is forever. You just have to get enough people to agree. Look at the current US situation. Things thought of as forever are now being shown to be much less permanent.