IBM's 3 year vest schedule on cash retention packages was 10% at 6 months, 10% at 12 months, 30% at 24 months, and 50% at 36 months. So half of your retention pay happens on the 3rd year anniversary.
It's only bad if the company is working toward some sort of an exit strategy. IBM isn't looking to sell itself, so putting in benefits and pay outs that encourage long-term retention makes a lot of sense.