Actually ILLYRIAN, you do bring up a good point. The film's Lothos we can disregard, but Lothos from the Origin comic book IS supposed to be canon.
The first few panels of issue 1 we are shown Lothos killing a Slayer during the Dark Ages (which ended roughly about 1,000AD) and he hints that this is not his first Slayer victim. From this we can gather that he is at least 1,000 years old.
In the comic all the vampire's features are more beastial than in the TV show, but Lothos in particular, while his normal appearance is very human, when he vamp-faces his facial lay-out changes considerably. See the picture below: