For the SSPX, priests are usually moved every five years. In The U.S., The District Superior (Fr. Rostand) will make recommendations for priests reassignment around the last week of June. He submits them to the Superior General (Bp Fellay) who makes the decision. The priest must also agree without condition.
IMHO,the SSPX considers itself a missionary order. It is felt beneficial that a particular priest not get too attached to a specific apostolate or chapel and that the faithful do not become attached to a priest.
For their part, the faithful, in general, appreciate the access to the Mass and Sacraments and while they certainly can grow fond of a certain priest, they can also find themselves welcoming a change.
For my own personal experience, I have admired and appreciated every priest and always warmed and became enthused with a new priest.
Last Sunday, our priest said “If you are coming here because of me, because you enjoy me or my sermons, you are in serious trouble”.
We must pray for every priest, especially the one that Baptized you, the one who gave you your First Holy Communion, the one that Confirmed you, The one that Married you or gave you Holy Orders, the one that will give you Extreme Unction, and the one who will bury you.