Bar-Mitzah Boys or Grown Ups?
From the Torah's description of the incident with Dena in Shechem (parshia C - 34:1-31), at least according to "pshat," Shimon and Levi must be at least in their late teens, while Dena must be at least twelve. [Even though Shechem refers to her once as a "yaldah" (see 34:4), the Torah consistently refers to her as a "na'arah" (see 34:3, 12).]

Now, let's do a quick calculation of the maximum age of Yaakov's children upon their arrival in Eretz Canaan:

Yaakov lived with Lavan for twenty years (see 31:41), but he only married Leah after working for seven years (see 29:18-23), i.e. thirteen years before his return home. Therefore, Reuven cannot be much older than 12, Shimon - 11, Levi - 10, and so on. Furthermore, Dena - Leah's seventh child (and remember - there was a break between Yehuda and Yisachar - see 30:9) - cannot be much older than five, and most probably even younger!

Even if Yaakov stayed in Succot for 18 months, as the Midrash writes (see Rashi 33:17), the problem still remains. Could the incident with Dena have taken place when she is in 'kindergarten' and Shimon, Levi, and the rest of the brothers have yet to celebrate their 'bar-mitzvahs?'

Thus, the incident at Shechem must have taken place at least five years later! This conclusion strengthens our original question. Why would Yaakov remain in Shechem for over five years without returning to Bet-El, without going home to visit his elderly parents?