for keeps

for keeps {infml} (for ever, or for always) — навсегда, невечно

Example 1: Once she moves in, she'll be there for keeps.
Example 2: Marriage ought to be for keeps. (LDOCE)

Example 2: Is it yours for keeps or does he want it back?

Related vocabulary:
[for the long haul]
[play for keeps]
[go the distance]