I'm sure you can edit the phone's software to do this, but if you don't mind running the battery down pretty quickly, but it would not be a good idea.
There should be an option in the phone's settings to keep the
LCD light on longer, but not all the time. I know that SOME phones, as long as they and plugged in wall or auto current, the
LCD will be on all the time, but never paid much attention to the models that do this, other than noticing that they do.