How long do you usually take to finish a KSP craft/project?

[magnemoe]

Depend on the complexity of project. My standard mining and science base in 1.02 took me a few hours.

I'm on day 3 of an eve accent craft.

Stuff like grand tour tends to take weeks.

[DMSP]

I just finished an Atlas V 551 W/ New Horizons in about an hour.

Uploading it tonight.

[mrclucks]

Payload for the kerbin system takes anywhere from 10 to 30 minutes while interplanetary payloads take half an hour to a full hour. Transfer and return vehicles take about the same time, and launch vehicles will take about a quarter of that time.

Then I launch and see how my launch profile goes, stage to my return vehicle and start reentry and see how my payload fairs under the atmosphere and how well my parachutes work. If everything goes successfully I may tweek a little to optimize a bit and if it doesn't go as planned then tweek more taking 10 to 30 more minutes. When I'm satisfied, I do my real launch so it takes somewhere between 20 minutes for a simplish rocket to 2 plus hours for a much more complicated one. Space stations will take much more time to optimize part count and resources and then you have to factor in any modules it will have and placement as well as tugs to move and/or rearrange it.