Being honest with time frames...
Once did a project scope for a large public sector organisation. We were called in to a big meeting to present our plan with a lot of people in the room who we didn't know (our big mistake). After running through the analysis and giving comparisons to similar projects we gave them a timeline of 6 months, which was roughly double what it should have taken but we couldn't guarantee they would complete their side of UAT on time.
A week later we found out that we had been kicked out of the account for "over-promising and lying" to senior management (we knew the techies within the organisation well).
Turns out a similar project was already in the works in a different part of the organisation, the owner of said project had been in our meeting. They were currently 2 years in and not even close to being finished. After being grilled by his bosses, he covered his ass by saying that we didn't know what we were doing and that it was significantly more complex than what we had stated (it really really wasn't).
Unsurprisingly he was an external contractor on a stupid rate and was hated by the internal IT team, but was old friends with someone in upper management.
This is why I hate doing work for the public sector.