Is the first impression always the last impression? I don't think so ... I usually start by liking people a lot, for me they can do no wrong, they all are inherently good and want or cause no harm to me or to anyone else in the society! but with every passing encounter and observations I discover things that i dislike and end up mostly disliking them altogether in most of the cases.
In the same was a friends of mine always starts with being wary of the people, she won't get too close or put too much trust in people or anything, she finds it very difficult to trust people and with every new interaction discovers the new and positive things about those once unknown.
we are not discussing here whose method of assessing people is better, but that we both don't retain the first impressions of the people we meet, we change them over time. we might remember what we first thought of them but that doesn't make us keep liking or disliking them. second thing that i have noticed and most people i discussed with disagree with it, that your appearances make a very big impact on how people perceive you, vanity may be but this is how i feel about people and the first impressions!