Hello,

May I stay a while?
Were you follong me a long time?
Wait a while.

I have seen these sentences(subtitles) in the movie named 'the double life of Veroniquie' and I would like to ask why they are not using 'for' before 'a while, a long time,...etc', what if I use 'for' before these? Does any different meaning occour?

May I stay for a while?
Were you follong me for a long time?
Wait for a while.

Thanks.