If you ever get your hands on a copy of
Giger's Alien, here are quite a few pictures where they have a number of Alien leggings hanging up side-by-side and the like. I think there are also images like that on the Quadrilogy.
The only time I've
ever heard of a film having one, and only
one, suit was
Species 3. Foam latex just generally isn't durable enough for one pull to last throughout the entire shoot.
(And Bolaji couldn't sit because of the tail, which on the original suit pointed straight down, not backwards like later suits. Had to sit on a swing
)