Not really a realistic idea considering some players are pulled away from the game by RL issues and sometimes are unable to return for weeks or months at a time. Life can be rough enough without having to return to your character being dead. This is supposed to be a game for people to enjoy, some of the players are casual RPers. It does not mean they do not care about their character but it does mean they do not have hours and hours to put in the game all at once. Sometimes the players have to be given a chance to be online at the same time in order to continue storylines they have started. Sorry, but forcing players to have their character's age by game time is not really fair to those that like the game but cannot invest time for consistent RPing. It is the gray area between RL players and fantasy world characters.
If you mean to base it off the number of hours that the character is logged in, that is also not really realistic. It takes time for players to consider their character's response, type it (not everyone is a fast typer), wait for someone that has gone afk, or waiting while a laggy player runs across the map for a predetermined meeting place to RP. Let's not forget about that lag monster and the crash monster that also cause interruptions of RPs...characters aging as they politely wait for a player to reply or get back into the system. All of these things add time onto a logged character and do add up after many many RPs. Not all RPs are rapid fire scenarios like tavern scenes. Some are thoughtful and slower paced. Some just take time. I did a fight scene with Jacula once...it took forever for us to type it out and make a great scene, but the game clock was ticking. There was also some OOC convos about things that were happening during the fight to make sure we felt it was within settings and reasonable. In other words we were having fun and didn't give a care how long it took on the game clock.
An interesting idea, but IMHO it is just not fair to penalize players with an 'artificial' wipe because of other game quirks that elongate RPs or RL issues that delay RP storyline progression.
When the devs are ready to wipe, they will do it.