We use the phrase, "once in a lifetime opportunity" to freely. Many things we label as, once in a lifetime, impact is to sick a degree it becomes something we return to regularly.
For example, traveling the world. A one off trip gets described as a once in a lifetime opportunity when what happens is you begin to prioritise and travel more often. Similarly a job opportunity comes along and is considered, once in a lifetime. Then more career opportunities arise.
In some ways life is Long time and there will be plenty of incredible opportunities. Love in such a manner you can embrace unique opportunities to grow your world view and live a full and varied love that contributes back into your community.