When Lavan first runs out to greet Yaakov, we are informed that he expected that he would be coming with wealth and gifts just as Eliezer had done Note that this implies that Lavan was quite old at the time that Yaakov ran away. We can calculate that Yaakov was 91 when Yosef was born based on the fact that he was 130 when he met Par'o (and Yosef was 39). Since Lavan was old enough to get involved with his sister's marriage, 20 years before Yaakov and Esav were born, this would imply that he was on the order of 40 years older than Yaakov. This puts Lavan at around 130 years (or more) at the time that Yoseph was born.
At the very beginning, Rav S. R. Hirsch points out that Lavan is forced to offer Yaakov wages because he realizes that he is such a good worker that he cannot afford to let him go by keeping him working for nothing while pretending that he is a guest. Lavan must feel relieved that "all" Yaakov wants is his daughter Rachel and yet he cannot stop himself form attempting to cheat him. Here is an example of how Hashem uses the impulses of the rasha to accomplish the goal that He has planned. At the end, when Yaakov is forced to flee, Lavan chases after him in order to confiscate his hard earned wealth and destroy the nascent family.
This is similar to the reaction of Mitzraim when they chased the Bnei Yisrael to the Yam Suf. It did not bother Par'o that they had taken the wealth as much as that they were no longer slaves to be worked to death. Based on the Midrashim that we have that describe the toil and suffering of the Bnei Yisrael in Mitzraim, we see that the Egyptians were very careful not to work them in order to actually accomplish something, but to break them body and spirit. This is why we have the medrash that the store cities were carefully built on swampy land so that they would constantly collapse and have to be rebuilt. This is why the actual tasks imposed were designed to be degrading rather than useful.
Contrast this with the relationship between Yisro and Moshe. From the very beginning, Yisro welcomes Moshe into his household. He sends his daughters to invite him to come in even when all he knows is that an Egyptian exile has helped them. He makes him a member of his household and offers him his daughter Tzipporah without any indication that he demanded anything from Moshe. It is purely a matter of his recognition that Moshe Rabbeinu would be a worthy husband of his daughter. Ont hte other hand, Moshe Rabbeinu takes up his position in the family without anything further needing to be said. The torah tells us that Moshe was with Yisro for some unspecified period of time that was "long". As it says in the Pasuk
ויהי בימים הרבימ ההמ
During those many days
Yet it then says that
ומשה רעה צאן יתרו חותנו כהן מדין
Moshe was herding the sheep of his father-in-law Yisro, the priest of MidianWe see that in spite of the long period of time involved, neither one of them saw any need to change to original unofficial "arrangement" between them. Moshe was in charge of the flocks and Yisro was concentrating on his position as the head of the state religion. We see the implication that Moshe was not just a plain shepherd, but was in charge of the flock form a number of places. First, the flock was sufficiently large so that the seven daughters had to have taken care of them even at the time that Moshe arrived. We have the medrash that one time a lamb ran away from the flock and Moshe chased it. How could he have abandoned the flock to wander by itself to chase a single lamb? When he saw the burning bush, he went aside to see what was going on. Again, how could he abandon the flock? When Hashem told him to go to Mitzraim, there is nothing in the Torah or in the medrashim about finding someone to take over his job.
We see from references in the Torah that both Lavan and Yisro had sons after Yaakov and Moshe arrived. In the case of Yaakov and lavan, these sons inflamed the jealous feelings of there father and attempted to make the situation worse. In the case of Yisro, we see from what happens later, that the sons continued to regard Moshe as an integral member of the family. Indeed, we see from the Haftarah of Beshalach that they came and settled among the Bnei Yisrael.
Yaakov had to run away from Lavan in secrecy and the "best" that could happen was to extract a promise never to cross the boundary between them and we say each year if the Haggadah than Lavan wanted to destroy us all. Moshe after receiving the call from Hashem, goes to Yisro to get his permission to leave. Yisro respond "Lech Leshalom". He sends him with good will and, when Moshe wants to send his wife and children to safety, he takes them back with no difficulty. When Bnei Yisrael are camped at Har Sinai, he comes to meet them and is greeted with honor and joy. He actively takes part is setting up the community and gives his best advice for the future of the people.His advice becomes the bsis for the entire judicial system of Bnei Yisrael and Moshe begs him to stay with them. As I said before, we see that the entire family comes and joins Bnai Yisrael. Besides the reference in Shoftim, we have a reference in the Talmud that descendents of Yisro were members of the Sanhedrin.
This shows the difference between a tzaddik and a rasha and the effect that they can have for the rest of time.
Update: Since Yisro was the priest of Midian, he was probably a Midianite. Midian was the son of Avraham and Keturah (Hagar). We can perhaps say that he fixed the flaws in Yishmael by coming back into the family of Avraham.
