in reply to My project estimates are based on:
For me Perl is a hobby (strictly for my own fun, or for fiddly things I can do "under the radar")
However I'm paid to implement SAP BPC systems and have found that no matter how optimistic or pessimistic I am in my estimate, the #1 rule is that the client will ALWAYS try and "negotiate" for less time. Initially I reacted by becoming more pessimistic and then delivering faster than planned, but found that clients aren't grateful ... they just take it as a sign you were planning to rip them off.
So now I estimate as accurately as I can, and when the client objects, I ask them to pick the functionality that's NOT going to be implemented.
Only one client has ever accepted the challenge ... and they decided they didn't need any project documentation! :-) ... I've since made more than 3 times the "saved" money out of them afterwards, because they had no idea how to support the system and had to keep calling me in.
blackstarr