http://www.premierleague.com/page/StatisticsSelect "All seasons" and it shows 7 clubs (Man Utd, Arsenal, Chelsea, Liverpool, Aston Villa, Tottenham and Everton) have all played the maximum 734 games, i.e. all have been ever-presents in the Premier League.
http://en.wikipedia.org/wiki/History_of_Arsenal_F.C._(1886%E2%80%931966)#Move_to_Highbury_.281910.E2.80.9325.29"Woolwich Arsenal moved there in the 1913 close season, having finished bottom and relegated back to the Second Division in 1912–13.[9] They replaced the "Woolwich" in their name with "The" in April 1914, finally becoming plain "Arsenal" in November 1919[16], although the press at the time continued to refer to them as "The Arsenal".[14]
The club controversially rejoined the First Division in 1919,[17][18] despite only finishing sixth in 1914–15, the last season of competitive football before the First World War had intervened — although an error in the calculation of goal average meant Arsenal had actually finished fifth,[19] an error which was corrected by the Football League in 1975.[20] The First Division was being expanded from 20 teams to 22, and the two new entrants were elected at an AGM of the Football League. One of the extra places was given to Chelsea, who had finished 19th in the First Division and thus had been already relegated. The other spot could have gone to 20th-placed Tottenham Hotspur (also relegated), or to Barnsley or Wolves, who had finished third and fourth in the Second Division respectively.[19]
Instead, the League decided instead to promote sixth-placed Arsenal, for reasons of history over merit"
I think the confusion is probably coming from the fact they've not been relegated since, which gives them the longest unbroken spell in the top division.
The confusion isn't surprising because with the various renames of the leagues, DW gets very confused when I start referring to pre-1992!
