I would like the phrase "Seize the night forever with me" translated
into latin. It will be engraved on a gift, if that helps with the
context. Since I need to have engraving done, an quick reply would be
greatly appreciated! Thanks!

What a romantic thought and even more romantic in Latin.
  
"Seize the night forever with me" translates as:

         Carpe mecum sempiterne noctem.

The word order is different from English, but the sentiment is just as sweet.

carpe = sieze, pluck, pick etc
http://www.archives.nd.edu/cgi-bin/words.exe?carpe

noctem = night
http://www.archives.nd.edu/cgi-bin/words.exe?noctem

sempiterne = eternally, permanently etc
http://www.archives.nd.edu/cgi-bin/words.exe?sempiterne

mecum = with me (combining form)

I also used Cassell's Latin dictionary:

Cassell's  Latin-English and English-Latin Dictionary revised by
J.R.V. Marchant, M.A. and Joseph F. Charles, B.A., Funk and Wagnell's
(New York)

I hope the gift is a big hit.

alanna-ga

Thank you very much - your help is truely appreciated!

As a starting point, a very basic, prosaic unnuanced translation might go:

Carpe Noctem Semper Cum Me


But I gotta believe there's a more elegant translation for you, which
I imagine some official researcher will provide soon.