Frankly, if you're marrying a person who requires you to spend 3 months on a diamond ring, it may be time to remember an important bit of wisdom:
Never enter into a contract where one party benefits by breaking it.
I'm not knocking marriage or (outright) stating that financial motives may be at play, here, but it's a big indicator if "who your with" is more concerned about what's "on their finger" than about what's "around their arm".
Depends on the law of your country, but the ring forms part of a contract, breach it and they have to give it back.
May be the least of your concerns at that point.
Never enter into a contract where one party benefits by breaking it.
I'm not knocking marriage or (outright) stating that financial motives may be at play, here, but it's a big indicator if "who your with" is more concerned about what's "on their finger" than about what's "around their arm".