Well, first of all, remote control over your computer is never completely safe. You never know who that person, who is taking over your computer is. The person can prove he is a real specialist only AFTER you grant the permission for the remote control over your machine. Also, once remote control session is established, the system becomes vulnerable to viruses and hacker attacks, for the ports that allow the remote connection are open. You risk to lose your saved files and folders, damage the system, make your machine running slowly. The viruses you might get during the session can lead to data loss or a complete break down of the system. Of course, it is more about trust. If you are sure that there is your own computer master on the other side, and this is the only option to get things done, for somebody of you two is not available physically at the moment - then it might be okay. But do not exclude the human factor. Your master might get distracted for a couple of hours, while your machine will be open for a hacker attack, etc. So, setting a time limit on the invitation for a remote assistance session might save you a lot.