Crickey!!!
The amount of run in depends on the type of rings used, the grade and type of oil used and the bore finish.
If you want to get a quality ring seal you have to wear the rings in to the honed surface in the bore to get maximum sealing and ring life.
If you use "barrel faced" chrome top rings, and a moly double rail style second, these need a very careful break in for the first 2 hours operation as with the reduced cylinder wall contact surface you get increased pressure per unit area of ring in contact with the bore. The smaller contact patch reduces drag/friction in the engine and helps get a better cylinder seal.
If you just give it heaps first off, the chances are the ring will over heat. If the ring gaps are not sufficient, the rings will seize in the bore. If the gaps are large enough, the rings will lose tension and cost you power and give blow by.

Normally I use a maximum of 20% throttle and Penrite HPR30 when cruising for the first hour, changing up and down as necessary.
Every 3 - 5 minutes give it full throttle for 5-10 seconds then allow about 2 minutes to cool down at very light throttle. Cruise for another 3 - 5 minutes before repeating.
The frquency of full throttle operation is gradualy increased over the next 3-4 hours operation and by that time the engine is fully bedded in with perfect ring seating on bore and ring lands.