I picked up my Hausa game from a week or two ago, it's 1503 now and still 20 more years until I get sufficient centralisation and innovation (didn't get a single helpful event...). I have 9 provinces (original Hausa 7 + Benin and Ashanti) and the rest of West Africa are my vassals, I have forts everywhere and they have mostly been built in their territories (my biggest vassal Songhai is lagging, but since they have Timbuktu and another bunch of cored rich provinces, it shouldn't take them long to fortify the rest of their lands). Question is: When to cross my tribal province limit and start absorbing those vassals? Bite the bullet now? Wait for my first NI (1507, almost there) and take Colonial Ventures? When my current Chief who's been in office for over 40 years dies? Maybe even wait until the 1520s/30s (if my ADM 5 50-year-old heir's heir happens to be good, that is...) when I get muslim tech?
Edit: So, I went with the variant of waiting for my king to die. Bad idea, the next guy lasted like 3 years and I am really struggling with that TSC (new chief is young and amazing with 8 ADM and DIP... and 3 MIL, ugh). Bad luck spawned the double size pretender stack in an inconvenient location and with a strong general. I haven't been able to take them on and barely managed to get them off my capital to protect Mr.ADM 8 with my entire combined forces (after the battle, I had 2k left, they were almost intact...). my manpower is in the trash, a three province Sokoto has revolted in my north, I at least seem to be winning that fight though since they are both far, far over their forcelimit and, unlike rebels, actually starve in my deserts. Inflation is quickly rising, manpower not really recovering...