Life Debts
Life Debts are one of the most misunderstood aspects of Wookiee culture.
First, the Life Debt is an obligation freely given by a Wookiee. Simply saving a Wookiee's life does not earn you a Life Debt. The Wookiee must feel endebted. If a Wookiee feels that they truly owe their life to another, they may choose to honor their benefactor with a Life Debt.
Life Debts are very rarely given to comrades in arms. In combat it is the duty of each individual to look out for their fellow soldiers, so most warriors do not give Life Debts for actions which occur in combat.
A Life Debt is not slavery. The Wookiee will chose how to honor the Life Debt and will determine when the debt has been repaid. A Life Debt does not obligate a Wookiee to do any acts against his/her will and the Wookiee should not be treated as a servant.
When a Wookiee feels they owe a Life Debt, it is best just to accept the honor. There is very little that will disuade the Wookiee from fulfulling his/her perceived obligation.
It is not unusual for a Life Debt to result in a life-long friendship between the Wookiee and the recipient. The best example of this transition is the friendship between Chewbacca and Han Solo. Chewie has long since repaid his debt to the smuggler. He now considers Han Solo to be his "fur brother" -- a member of his honor family.