Is MLS mistaken in signing coaches long term?

This is something I've been thinking about....In leagues that have two championships a year (apertura/ clausura or invierno/verano) they hire coaches or only six months after which they evaluate the coach's performance (if they don't just get sacked midway through the season).
In European leagues, coaches (for the most part) are signed for a year and then renewed or let go with respect to how they do.....(with some sackings also occurring throughout the season)
MLS is a ten-league team, therefore MLS coaches can be pushed to perform their hardest by the pressure of being replaced if they fail to produce...However, coaches like those at Dallas and LA (to name two teams not doing well) have long-term contracts that not only might be making them feel too important and above reproach, but also can hinder the league's willingness to remove them from their positions (for financial reasons). After all, it was only a few months ago Sigi got signed to a multiyear deal. Whether a coach gets the MLS Cup or not, i do not see why contracts can't limit themselves to one year only, forcing coaches to perform year after year, and not fall asleep based on previous accomplishments....It's not like our coaches are willing to go to lower divisions here in America, nor are they in great demand abroad