Assuming that you were still married when your husband passed, there is no time limit for marriage. As long as you were married when your husband passed you are eligible to collect from his Social Security. A widow/widower can collect FULL benefits at Full retirement age or reduced benefits as early as age 60. A disabled widow/widower can collect as early as age 50 (if found disabled by SSA). However, if your own benefit is higher than his you may not recieve his benefit. You are only entitled to the higher of the two benefits.
If you were divorced, you would need to have been married for at least 10 years before you can draw a spouse or deceased spouses benefits.
The attached link is to the Social Security Website which outlines Survivor's Benefits as I described above
I hope this is helpful to both you and the other interested responder.