Quietrebel
We're probably in a similar situation to you (DW EU national, DCs British). In March last year we started applying for the PR card for DW (who's been here for 40 years) and after an initial rejection we sent documentation measured in kilos, not pages. Initial rejection took 3 months to come through, then additional time collating all the evidence and redoing the form.
Finally got PR card in November, although it sais she'd been here only since 2011, not 1978 as is actually the case. We then realised there's nothing "permanent" about it - if we leave for more than 2 years, she'll lose her PR rights. So started citizenship process (language test, Life in UK test, both passed at first attempt) and submitted appropriate lengthy form & supporting documentation (plus £1330 admin fee!). We then got a notice requesting biometric enrolment, which can only be done in certain Post Offices. Did the deed, PO confirmed the biometrics had been sent, then waited for a while. Then got another letter saying we'd failed to provide the biometric details. Wrote back with copy of receipt from Post Office, received reply saying our application had "been unsuccessful in the system" (whatever that means, but basically it was our fault we'd failed).
So back to PO, did biometrics again and asked for comfirmation from HO that they'd got the information this time. No answer as yet, so still waiting. All in all, it's taken almost 18 months to date, paid out over £2000, jumped through every hoop in sight and we still don't know whether DW will get her British citizenship.
When (If!) we do finally get the UK passport, we'll probably move back to Germany anyway, although we have no family or friends there any more (40 years is a long time). We just need UK citizenship in case Germany doesn't work out and we need to come back. And a vote, of course, which she never had in the Referendum which has turned our lives on their head.