Fair enough. My impression of the SWB literature is that the relationship is robust, both in a purely correlational sense, and in papers like the Frey and Stutzer one where they try to control for confounding factors like personality and selection. The only major catch is how long it takes individuals to adapt after the initial SWB spike.

Indeed, having now managed to track down the paper behind your first link, it seems like this is actually their main point. From their conclusion:

Our results show that (a) selection effects appear to make happy people more likely to get and stay married, and these selection effects are at least partially [emphasis mine] responsible for the widely documented association between marital status and SWB; (b) on average, people adapt quickly and completely to marriage, and they adapt more slowly to widowhood (though even in this case, adaptation is close to complete after about 8 years); (c) there are substantial individual differences in the extent to which people adapt; and (d) the extent to which people adapt is strongly related to the degree to which they react to the initial event—those individuals who reacted strongly were still far from baseline levels years after the event. These last two findings indicate that marital transitions can be related to changes in satisfaction but that these effects may be overlooked if only average trends are examined.