Why are some questions locked?

looks like it's just a matter of how old they are

The forum locks questions to prevent spam after they are posted for a certain period of time. This keeps users and the site itself safe and managable. Furthermore, people can use old post to farm experience, as was a problem with Reddit a while back, I remember when the site was down :)

If you want an old question temporarily opened you can privately message a moderator and request it.