If 4 years ends up being the cut-off for free agency then it'll be a farce. Why would clubs put their money and resources into drafting and developing youngsters only to lose them just as they start cementing a senior spot.
All it will mean is players will get paid a market rate. I really don't think many of them will leave, maybe they will, but that will help teams like richmond who are 9th buy a few good players and get to 8th. I mean players that teams don't want to lose but aren't willing to pay for them, like Lake from the dogs. As long as the salary cap is sacrosanct and is enforced rigorously I think it will benefit the evenness of the league. Otherwise we'll go back to carlton vs collingwood and St Kilda will get the wooden spoon for the next 20 years.
If we find it doesn't benefit the evenness of the league then I'd be all for getting rid of it after a trial period.