Is it safe to allow remote desktop and remote assistance to be on – I am just an average home user. Dell did help me with an issue and they used it … but is it safe to leave on all the time?
There isn’t any need for the program to be on all the time it it is an open door that with the right information
can allow access to your computer.
It’s a tool to be used when needed and once it’s served its purpose, shut it down. IMHO 
I would also say it is a tool that should only be enabled when you need to use it. There is also another one, Remote Registry and that too is disabled on my system unless it is required.