So I have been logging about 120 hours into Civ 5 and just some questions about taking my play-style to the next level. I now win consistently on Prince difficulty, but feel like I take too long to finish the games.

1. I have seen quite a few pictures now of people having like 600 science by turn 280 . Is that due to playing on quick game speed or are there certain specialist/city manipulations I should be going for? I usually go for the GL rush, and feel that really helps in the beginning, but after that I can feel the science start to pile up.
2. About how long should each game take per victory type? I know it can differ quite a bit due to a lot of factors, but again I feel like I could be playing a lot better to help close out the game faster. If there isn't a good answer for this, then how long would you say it takes you to finish for each type?
3. Is it good to manually assign specialists when you have the chance? I have already gotten into the habit of setting my cities to Production mode, but I haven't really looked into assigning specialists just yet.
4. How many cities do you usually build when going for a science victory? What about Culture? I feel like I tend to build few too many cities and I think that usually bites me during the end game.
5. About how early do you start attacking other civs when going for a domination victory? I tend to go around turn 90-100 when I feel like I will have no problem taking them.
6. Is it a good idea to focus your workers on tiles occupied by civilians and then work the non-occupied tiles when you know you have time?
7. What is your usual starting production build order for any type of game? If that doesn't really offer a good answer then what is your build order for each type of victory? Again, I know that this answer can differ by quite a bit but I am curious to see everyone's possibilities are.
8. This might be an obvious question, but is it better to research more-so towards your victory path or just try and balance things out? I know in the early game I try to at least balance a few things out when going for a culture/science victory, but would it be better to leave the other techs in the dust if it isn't really needed for my victory path?

Sorry for all the questions, I am just really curious as to how I can improve my game and I really wanted to see everyone's recommendations for how I can to that. Thanks!