The stories from Round 1 (e.g. @jot) scared the bejeezus out of us, we spent a solid Sunday getting every scrap of paper to prove our expenses (from invoice to credit card to bank account to our names on a bank statement proving ownership). They're more on top of the process now than in Round 1, we did have to get some extra docs but it just involved a few phone calls back home.
I believe for Round 3 it is a bit easier and I'd expect it to keep improving. Assume 1-2 days admin on this every month regardless (just with less follow-up stress after you submit your docs).