I had 1000gs in a about 4 hours 15 mins, i had the guide nest to me for the collectables, and only went for one thing at a time (high score one run, collectables, and gates) just complete one level and move onto the next, i also didn't bother to change boards or characters at all through the game, so its pretty easy to do the whole thing with the starting board.
If it ain't broke... Modify It !!
100% Retail: 63 I 100% Arcade: 27 I 100% WP7: 6
GS: 15k (27/01/11) 30k (29/9/2011) 60k (8/10/12) 100k (22/11/13)
15x 360 consoles, 240+ retails games