Many wedding invitations written in Hebrew that I've seen have the abbreviations נ"י - after the groom's name - and תחי' - after the bride's name. (Example) Sometimes they are slight alterations on those themes. (Example?)
- How/why did this standard arise?
- Why are there different abbreviated good wishes for males and females in this context?
- Does the difference extend to other contexts?
The bold one is the main question, but I think it likely that a good answer to it will also answer the other two.