How many jewelry store ads have you seen (especially during February, June and December) that try to tell you that you should spend "two months' salary" -- at least -- on an engagement ring? Then there's the $25,000 you'll probably have to spend on the wedding... 

For most of us, that's just not possible, and it leaves many men worrying that their potential brides will see them as cheapskates if they spend much less.

Well, worry no more -- at least not nearly so much.

A new study by Andrew M. Francis and Hugo M. Mialon called "'A Diamond is Forever' and Other Fairy Tales: The Relationship Between Wedding Expenses and Marriage Duration" has found that the diamond equivalent of a boulder will not necessarily cement a long and happy union.

In fact, it is statistically likely to lead to a shorter one.

That doesn't mean that you should go absolutely minuscule, though; marriages that began with a ring that was too inexpensive are also shorter on average. A good rule-of-thumb is to spend between $500 and $2,000.

A similar correlation was made between the cost of the wedding itself and the length of the marriage. Weddings that cost less than $10,000 (a good $20,000 short of the American average) are more likely to lead to a long marriage than those that cost more.

Other factors that seem related to the enjoyment of a longer marriage are having a long guest list and a honeymoon -- one you can afford, regardless of cost or destination.

Studies aside, here's something to also keep in mind: if there's an heirloom in the family -- say, a great-grandmother's engagement ring from your side or hers -- that the current owner doesn't mind passing along, jump on it. It costs nothing but a professional cleaning and maybe a re-sizing, but it will mean more to her than even the Hope Diamond ever could.