Adam LaRoche in 2012 was very good. He had career highs in homeruns and RBI, but he also had a career high in plate appearances. In actuality LaRoche's 2012 batting line of .271/.343/.510 wasn't that far off from his career batting line of .268/.338/.482. Many people refer to 2012 as a career year for Adam LaRoche, but in order for it to be that it has to be the best year of his career and it isn't. In 2006 Adam LaRoche hit .285/.354/.561. Thus far in LaRoche's career his career year is 2006 and it is likely to remain that way as he heads into the last couple years of his prime. In no way was 2012 a fluke or anything that should lead one to expect a significant drop off from LaRoche.
LaRoche's mean is his career average of .268/.338/.482, and while he is going to be 33 during the 2013 season he shouldn't start to truly decline until around 35. Combine regression with decline and LaRoche's 2013 numbers shouldn't be far off from his career average, but perhaps a little below. Bill James projections have him at .256/.334/.471 and that just kind of feels right. LaRoche is a solid hitter and it is known what he can give a team. He has reached the stage in his career where he has settled in to being what he is.
There is more to LaRoche than just offense though and defensive numbers indicate that LaRoche has gotten better as his career went along. In his best offensive season of 2006 he was a -4.6 UZR fielder, but in 2012 he finished the season with a UZR of 6.1 and fWAR of 3.8. Let's pull back a second and remember that both UZR and WAR are in someways based around league averages. In 2006 a MLB average first baseman hit .285/.363/.488 and in 2012 .262/.336/.442. In 2006 Adam LaRoche was below average in batting average and in on base skills, but in 2012 he was above average in both those areas, and not because LaRoche was a better player, but because the average MLB first baseman was worse.
In 2006 the top five first baseman in baseball by fWAR were Albert Pujols (8.5), Lance Berkman (6.2), Ryan Howard (6.2), Nick Johnson (5.3), and Justin Morneau (4.0). In 2012 the top five in baseball were Prince Fielder (4.9), Edwin Encarnacio (4.4), Albert Pujols (3.9), Adam LaRoche (3.8), and Paul Goldschmidt (3.7). Look at the list from 2006 and the one from 2012. Many of the top first baseman from 2006 are either nearing the end of their careers or have suffered injury issues. Albert Pujols is one of the only players to be on both lists and 2012 is considered one of his worst seasons, but yet he was still a top five first baseman. Adam LaRoche isn't a better first baseman now than what he was in 2006.
Adam LaRoche in 2012 was a top five first baseman not because he was so much better than his career averages, but more that baseball had come down to his level. 2013 shouldn't be all that different from 2012. LaRoche should regress a little to his career levels and factor in a moderate bit for decline and what you have is much the same LaRoche as Nats fans saw in 2012. He may hit one less double and homer a month and might have one or two less walks a month, but it won't be a noticeable difference. Aside from 2011 Adam LaRoche has been one of the most consistent and durable performers in MLB, and there is no indication that that shouldn't continue in 2013.