The problem with term limits is that we have congressional rules which reward incumbency. The more seniority an incumbent has, the more likely they are to chair committees, decide on rules for hearings, and exercise power. This system also puts unfair hurdles in front of potential challengers. Long term incumbents enjoy touting seniority as a motive for retaining office, while the challenger obviously has none. Committee leadership should be chosen by lottery of interested participants. This would negate the "seniority" factor in campaigns, holding incumbents solely to their record of service.
I do not favor hard term limits as it works against democratic choice. If voters want a representative for life because that representative is excelling at their position, then the voters should have that option.