I think extending the amount of time wasted before a player is automatically eliminated would be a bad idea.
At some point the needs of the majority of the players to not have to play in a game with interminable delays has got to outweigh the right of a single player to take an inordinate amount of time between turns.
The issue is really the right of all players to expect resonable delays in the game versus the right of a single player to participate in a game in which he really cannot participate.
At some point you have to tell the person who wants to participate knowing he cannot take his turns in a timely (24 hour) period that if he were allowed to participate (without penalty) he would essentially be ruining the thing in which he wants to participate.
It really is as simple as not starting games a week or two before your vacation and then resuming playing the moment you get back. To expect otherwise is to impose the cost of your vacation on the other unfortunate players who happen to be in games with you.
A possible enhancement to the game would be to allow people to specify the turn duration during the creation of the game. For example,
Turn Duration: o 1 day o 3 days o 7 days
At least this way you would know what you're in for when you start a game.
Doing what you want is fine and good up to the point at which you are causing others undue suffering by your actions (or inactions in this case).