I try to ensure that I have unbroken census coverage for a family. That is; I try to obtain records for each possible census year, showing each parent from marriage to death and each child from birth to marriage. One of my reasons is to ensure that I identify all the children. Another is that the names, ages and locations help me ensure I have the correct family and identify approx. BMD dates (I also try look at wills and testaments to corroborate my findings.)
Given the expense in obtaining image records from pay-for-view sites, I'd like to avoid using them when I can safely do so. Are there any typically justifiable circumstances for using freely available census transcriptions, such as those at FamilySearch? I've never really seen this discussed before.