I have 950 subjects. I have almost no missing values for any variable except age. I am missng about 25 of them. I haven't formally analyzed them yet but I have a suspicion they are not missing completely at random. I suspect it is the older subjects who declined to answer the question.
So, when I adjust for age in LR, I loose the 25. I could either leave it as missing, substitute the average age or substitute the average age for their level of experience (experience and age were highly correlated).