In the general case, this is to prevent a user from posting a bunch of questions about some topic without doing enough research on it. You can see this happen even with experienced users. I know of a couple of high rep users who often did/still do this, one with 10k+ rep, one 1k+ - they'd grab some new topic and then we'd see a bunch of usually trivial questions on it. And not just on AU, but spreading their posts over U&L and SO as well. Without question limits, I have no doubt we'd see dozens of low-quality posts spammed all over the network from high-rep users.
I don't think new Ubuntu releases merit an exception for this. If the problems that you have answers for are truly that important, other users will post questions about them sooner or later. Just answer then. Or, find questions about the same problem which differ only in the Ubuntu version, and answer there. It's a common practice here to generalise questions beyond a specific release if possible, so that's fine. (This IMO is the best option for software-installation questions.)
In the meantime, prioritise. Decide which of the problems you don't have answers to are most important and post those. It's just a new Ubuntu release that's not being forced on anyone. There's no real need to raise the limits for that.