Effen makes a bunch of great points about the differences in complexity in plans as well as the potential differences in the quality of 5500 filings.
There are additional things to consider as well, are you using Datair Pension Reporter? Is everything being entered by hand? Do you have an automated or semi-automated process in place? Are you including review time? What level of review does your firm require (clearly an actuary is reviewing the sch sb, but is the 5500 peer reviewed? actuary reviewed? The AFN?)?
All of that being said at my former employer where we used datair as a val system, but ftwilliam for 5500 filings and had a mostly automated process in place for the sch sb I would guess that in pure prep time your estimate would be a little high. We did a ton of 3rd party actuarial work and with the processes that we had in place a junior admin could prep a sch sb and afn in 40 minutes or so (again this is a pure vanilla plan, no surprises). We had one whiz kid for a while that liked to time himself, he was under 20 minutes for a sch sb and under 30 for sch sb and afn. I would guess that 5500SF, sch sb and afn would have been 1.5-2 hours. This is assuming val is done, contributions confirmed, trust reconciliation complete, etc. before work is started.
But to go with that we had a very robust review process that ensured that all the i's were crossed and t's dotted. I would guess that review would add anywhere from 10 minutes to 45 minutes depending on which actuary was reviewing.