My sims' partner choices are only mine to make since I play solely for genetics. I do ensure that their partners are compatible and, because of this, they roll only wishes for each other. All my friendly sims roll wishes to meet someone new constantly and I don't read this as meaning that they want to move on, rather than that they want to widen their circle of friends. My sims will also roll wishes to be friends with X if the relationship level drops below friendship for some reason - usually because my sims have had a negative encounter with a sim with bad traits who caused the drop in the first place. I see wishes as game hints rather than any meaningful desire on the part of the sims although I do project my own feelings when it suits me, for example when my loving couples roll romantic wishes for each other it makes me feel like I chose the right partner for them and that they are happy.