If your sole measure of advantage is promotion then yeah, feel free to kick back your heels and do whatever you want.

Personally, I quite like to be doing useful work, and normal ramp-up times for people seem to be about 3-6 months, which if you work at a company for < 3 years can be as much as 10-20% of your time. More if you're switching between projects within a company. It's pleasant to not have to waste that large a percentage of your time getting up to speed.