I'm going to continue a relationship I know won't last
Why stay in a relationship you know won't last?
Because I don't want to spend my entire life with someone.
It's not nice to lead someone on like that. If you don't love this person anymore you should just leave.
Love? What are you talking about? It's just a relationship of convenience.
You're wasting your partner's time by deceiving them. It's better if you break up with them and find someone who is also not looking for a long term relationship.